Clock Generator
Specification for
AMD64 Processors
Publication # 24707 Revision: 3.08
Issue Date: September 2003
© 2002, 2003 Advanced Micro Devices, Inc. All rights reserved.
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24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Contents
Revision History...............................................................................................................................3
Chapter 1 Description................................................................................................................5
1.1 Specification Overview......................................................................................................5
1.2 Pin-Strapped Configuration ...............................................................................................5
1.3 Processor Frequency Selection and Spread Spectrum Clocking .......................................5
1.3.1 Reserved Test Mode Operating States.......................................................................6
1.4 Differential Push-Pull Processor Clock Outputs ...............................................................6
1.5 Selectable 33-MHz or 66-MHz Clock Outputs .................................................................6
1.6 PCISTOP33_L Control Signal...........................................................................................6
1.6.1 Starting the 33-MHz PCI Clocks ...............................................................................6
1.6.2 Stopping the 33-MHz PCI Clocks .............................................................................7
1.7 Input Reference Crystal Definition....................................................................................8
1.8 Internal Input Pullup Resistors ..........................................................................................8
1.9 Software Interface and Control..........................................................................................8
1.9.1 Hardware Selection with Software Programmable Overrides ...................................8
1.9.2 Configuration Read-Back ..........................................................................................8
Chapter 2 Features.....................................................................................................................9
Chapter 3 Frequency Selections .............................................................................................11
Chapter 4 Logic Block Diagram .............................................................................................17
Chapter 5 Pin Locations and Descriptions ............................................................................19
Chapter 6 Package Pinout – 48-Pin SSOP.............................................................................23
Chapter 7 Electrical Specifications.........................................................................................25
7.1 Absolute Maximum Ratings ............................................................................................25
7.2 Operating Conditions.......................................................................................................25
7.3 Electrical Characteristics .................................................................................................26
7.3.1 Logic Inputs .............................................................................................................26
7.3.2 SDATA, SCLK Input/Output ..................................................................................26
Contents 3
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
7.3.3 X1, X2 Crystal Input/Feedback............................................................................... 26
7.3.4 PCI/ HyperTransport™ Clock Outputs................................................................... 27
7.3.5 REF[2:0] Clock Outputs.......................................................................................... 29
7.3.6 USB, 24_48MHz Clock Outputs............................................................................. 30
7.3.7 CPUT[1:0], CPUC[1:0] Clock Outputs .................................................................. 32
7.3.8 Differential Processor Clock Motherboard Termination Scheme........................... 34
7.3.9 Differential Processor Clock Input......................................................................... 35
7.3.10 Differential Processor Clock for AMD64 Processors Test Load............................ 36
7.4 Spread Spectrum ............................................................................................................. 37
7.5 Skew................................................................................................................................ 37
Chapter 8 SMBus Interface.................................................................................................... 41
8.1 SMBus Protocol .............................................................................................................. 41
8.1.1 Block Write ............................................................................................................. 41
8.1.2 Block Read .............................................................................................................. 41
4 Contents
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
List of Figures
Figure 1. PCISTOP33_L Control Signal ...........................................................................................7
Figure 2. Processor Clock Logic Block Diagram ............................................................................17
Figure 3. SSOP Package Pinout.......................................................................................................23
Figure 4. Single-Ended Measurement Definitions...........................................................................33
Figure 5. Four-Layer Motherboard Stack-Up and Impedance.........................................................34
Figure 6. Motherboard Processor Clock Termination Scheme........................................................35
Figure 7. Target Processor Internal Bias Generation.......................................................................36
Figure 8. Differential Processor Clock for AMD64 Processors Test Load .....................................37
List of Figures 5
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
List of Tables
Table 1. System Clock Features........................................................................................................ 9
Table 2. Frequency Selections ........................................................................................................ 11
Table 3. Pin Locations and Descriptions......................................................................................... 19
Table 4. Absolute Maximum Ratings ............................................................................................. 25
Table 5. Operating Conditions ........................................................................................................ 25
Table 6. Logic Input Electrical Characteristics............................................................................... 26
Table 7. SDATA and SCLK Input Electrical Characteristics *...................................................... 26
Table 8. Crystal Input/Feedback Electrical Characteristics ............................................................ 27
Table 9. PCI/HyperTransport™ Clock Output Electrical Characteristics
(Lump Capacitance Test Load =30 pF)............................................................................ 27
Table 10. Reference Clock Output Electrical Characteristics
(Lump Capacitance Test Load = 20 pF) ......................................................................... 29
Table 11. 24_48 MHz, USB Clock Output Electrical Characteristics
(Lump Capacitance Test Load = 20 pF) ......................................................................... 30
Table 12. Processor Clock Output Electrical Characteristics ......................................................... 32
Table 13. Board Stack-Up Parameters ............................................................................................ 35
Table 14. Spread Spectrum Characteristics..................................................................................... 37
Table 15. Skew Characteristics ....................................................................................................... 38
Table 16. I2C Address ..................................................................................................................... 42
Table 17. Byte0: Frequency and Spread Spectrum Control Register.............................................. 42
Table 18. Byte1: PCI Clock Control Register (1=Enabled, 0=Disabled) ....................................... 43
Table 19. Byte2: PCI Clock, USB, 24_48MHz, REF[2:0] Control Register
(1=Enabled, 0=Disabled)................................................................................................ 44
Table 20. Byte3: PCI Clock Free Running Select Control Register ............................................... 44
Table 21. Byte4: Pin Latched/Real Time State (and One Free Running Control)......................... 45
Table 22. Byte5: Clock Vendor ID ................................................................................................. 45
Table 23. Byte6: Reserved for Byte Count ..................................................................................... 46
6 List of Tables
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Revision History
Date Revision Changes
September 2003 3.08 Fourth Public release.
September 2003 3.07 Changed the title of the document to “Clock Generator Specification for
AMD64 Processors” and changed references throughout the document.
November 2002 3.06 Third Public release.
November 2002 3.05 Added note in Table 2 for resistor strapping recommendation.
Made changes in Table 3 for pin descriptions section of FS(2:0) signals.
November 2002
3.04
Changed the title of the document to “Clock Generator Specification for
AMD Athlon™ 64 and AMD Opteron™ Processors” and changed references
throughout the document.
September 2002 3.03 Second Public release.
September 2002 3.02 Internal revision.
August 2002
3.01 Changed the title of the document to “Clock Generator Specification for
AMD Athlon™ and AMD Opteron™ Processors Based on Hammer
Technology” and changed references throughout the document.
August 2002 3.00 Initial Public release.
Revision History 3
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
4 Revision History
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Chapter 1 Description
This specification is intended to provide a definition of the minimum set of requirements for the
first AMD64 processors system clock generators.
1.1 Specification Overview
The goal of this specification is
• to provide enough information to enable development of clock generators for the
AMD64 processors
• to provide the definition of a minimum feature set for a clock generator that enables initial
platform shipments
• to allow clock generator vendors the flexibility to provide product differentiation above and
beyond this minimum feature set
• to provide backward compatibility with AMD Athlon™ processor-based platforms
1.2 Pin-Strapped Configuration
Upon power up, the device samples the input states of various configuration input pins to define
the correct operating state without the need for software configuration through the I2C interface.
The I2C interface to internal configuration registers provides a method to optimize the operating
state of the clock generator.
Note: Changes made through the I2C interface will override the hardware pin strapped
configuration.
1.3 Processor Frequency Selection and Spread Spectrum
Clocking
Processor frequency selection of 100, 133, 166, and 200 MHz are defined from hardware-sampled
inputs. Additional frequencies and operating states (combinations of processor frequency and
spread spectrum clocking features) can be selected through the I2C programmable interface. The
specified features in this specification provide a minimum set for AMD64 processor-based
platforms. Additional features may be provided at the discretion of the clock generator
manufacturer.
Spread spectrum modulation (down-spread only) is required for all outputs derived from the
internal processor PLL as shown in Figure 1 on page 7. This includes the processor, PCI33 and
PCI33_HT66 outputs. The REF, USB, and 24_48 MHz clocks are not affected by spread
spectrum control. The spread spectrum requirements include the ability to enable and disable
0.5% down spread clocking. A 0.5% down spread, 33-kHz triangular modulation is required and
Chapter 1 Description 5
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
other spread amounts less than 0.5% down spread and less than 50 kHz ∆f/∆t modulation are left
to the clock generator vendor to include as differentiating features.
1.3.1 Reserved Test Mode Operating States
This specification defines two test modes and reserves one other for the purpose of providing
required system debug and system test operating modes. The reserved manufacturer test mode is
provided for each clock vendor to implement an operating mode specific to their own production
test flow needs and is not required for system operation.
1.4 Differential Push-Pull Processor Clock Outputs
This clock generator is specified to provide push-pull driver type differential outputs for the
processor clocks (2-pair) instead of the common open drain style used for AMD Athlon processor-
based platforms. This provides a more testable product and results in less variation in edge rate
and differential skew as seen by the processor. The processor clock termination scheme has been
derived such that 15–55 ohm, 3.3-V output drivers can be used for the processor clocks.
1.5 Selectable 33-MHz or 66-MHz Clock Outputs
This clock generator specification defines a number of clock outputs that are selectable between
33 MHz and 66 MHz. This selection provides flexibility across platforms that may implement a
combination of 33-MHz PCI resources, 66-MHz PCI resources, and HyperTransport™ technology
resources.
Note: HyperTransport technology is the HyperTransport Technology Consortium’s next
generation interconnect technology that is designed for use with all AMD64 platforms.
1.6 PCISTOP33_L Control Signal
This clock generator specification defines one asynchronous PCISTOP33_L signal that provides
control for 33-MHz output clocks. Both the PCI33 and PCI33_HT66 clocks, while operating at
33MHz, must stop in response to PCISTOP33_L assertions. While operating at 66 MHz, the
PCI33_HT66 outputs are not affected by PCISTOP33_L assertions.
The 33-MHz PCI clock outputs, once stopped, should be in the Low state and started with a full
high-pulse width specified. The 33-MHz PCI clock outputs on latency cycles are only one rising
PCI clock turned off. Latency is one PCI clock. Section 1.6.1 and Section 1.6.2 on page 7, along
with Figure 1 on page 7 gives a description and timing diagram respectively, of the required
timing sequence:
1.6.1 Starting the 33-MHz PCI Clocks
The 33MHz PCI clocks must be started using the following sequence of events:
6 Description Chapter 1
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
1. On a given PCI clock rising edge, the PCISTOP33_L signal is asserted (first arrow from the
left in the timing diagram).
2. On the next rising edge of the PCI clock, the clock synthesis chip samples PCIST0P33_L
deasserted (second arrow from the left).
3. The PCI clocks start running with the next rising edge of the PCI clock (third arrow from the
left).
1.6.2 Stopping the 33-MHz PCI Clocks
The 33-MHz PCI clocks must be stopped using the following sequence of events:
1. On a rising edge of the PCI clock, the PCISTOP33_L signal is asserted (4th arrow).
2. On the next rising edge of the PCI clock, the clock synthesis chip samples PCISTOP33_L
asserted.
3. On the next falling edge of the PCI clock, the PCI clocks go Low and stay Low.
Figure 1 is a picture of the PCISTOP33_L control sequence. All numbered arrow references are
counted from left to right.
Figure 1. PCISTOP33_L Control Signal
Note: The fifth arrow, from the left, shows there is no rising edge on the stopped PCI clocks.
Chapter 1 Description 7
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
The following notes give additional information on the PCISTOP33_L control sequence.
Notes:
1. All timing is referenced to internal CPUCLK.
2. PCISTOP33_L is an asynchronous input.
3. All other clocks continue to run undisturbed.
4. PCI33_HT66SEL_L is shown in the High state.
5. PCISTOP33_L must meet 10 ns setup/hold times.
1.7 Input Reference Crystal Definition
The crystal inputs and pin loading should be compatible with 18-pF crystals.
1.8 Internal Input Pullup Resistors
This specification defines internal pullup resistors on most of the control inputs. The internal
input pullup resistors allow the input pins to be left unconnected in applications where their
function is unnecessary. Additionally, these input pullup resistors provide the required pullup for
open drain-type outputs for SMBus. The general range of values is provided for these internal
pullups.
1.9 Software Interface and Control
Software interface and control of the clock generator are described in Sections 1.9.1 and 1.9.2.
1.9.1 Hardware Selection with Software Programmable Overrides
Configuration of the features of the clock generator can be completed through hardware pin
strapping alone or by hardware pin strapping with optimization of features through programmable
registers accessed through the SMBus interface. The values of the programmable registers will
override any hardware strapped settings, once the settings are changed.
1.9.2 Configuration Read-Back
The values of the programmable registers can be read back through the SMBus interface to allow
the current operating state of the device to be determined.
8 Description Chapter 1
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Chapter 2 Features
This specification describes the main clock generator for AMD64 platforms. Table 1 describes the
system clock features.
Table 1. System Clock Features
Features Frequency Type Voltage
Two differential pair processor
clocks
200-MHz, 166MHz, 133-
MHz, or 100-MHz
Differential
push-pull
3.3 V
Six PCI clocks 33-MHz Push-pull 3.3 V
One free running PCI clock 33-MHz Push-pull 3.3 V
Three AGP/HT clocks 33-MHz or 66 MHz Push-pull 3.3 V
USBCLK 48-MHz Push-pull
3.3 V
FDC clock 24-MHz or 48--MHz Push-pull 3.3 V
Three Reference clocks 14.318-MHz Push-pull 3.3 V
Additional features of the system clock are as follows:
• 3.3-V operation
• Two true differential processor clocks pairs (supports both 1P and 2P platforms)
• Seven 3.3-V dedicated 33-MHz PCI clocks, one free-running
• Three 3.3-V selectable 66-MHz or 33 MHz clocks to be used for HyperTransport™
technology reference clocks or PCI 33-MHz clocks
• One 3.3-V 48-MHz output for USB
• One 3.3-V 24-MHz or 48-MHz for SIO
• Three 3.3-V 14.318-MHz reference clocks (one additional to provide reference to external
24.576 MHz generator if needed for AC97 codecs)
• EMI Suppression using spread spectrum technology (down spread only with 33 kHz triangular
modulation)
• SMbus interface for configuration register programming and read back (Rev 1.0)
• Power management control inputs
• A 48-pin SSOP
Chapter 2 Features 9
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
10 Features Chapter 2
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Chapter 3 Frequency Selections
This chapter contains frequency selections for the Clock Generator and they are shown in Table 2.
Table 2. Frequency Selections
Input Configuration
Processor
(MHz)
PCI33 (MHz)
PCI33_HT66
(MHz)
24_48
(MHz)
14.318
(MHz)
Comment
FS2
FS1
FS0
PCI33_HT66
SEL_L
PCI
STOP33_L
24_48SEL_L
1 1 1 X 1 X 200 33 33
or
66
24 or
48
14.318 Normal
AMD64 Processor
Operation
1 1 0 X 1 X 166 33 33
or
66
24 or
48
14.318
Reserved
Notes:
1. During bypass mode the X1 input pin can be driven with an external clock signal from 10 MHz
to 100 MHz. This mode is used in system debug for frequency testing and is planned to be used
in the smart burn-in systems for the AMD64 processors used for production burn-in capability.
2. These operating modes are reserved for vendor specific test requirements and may be different
from vendor to vendor. These modes will not be used in the system.
3. In these cases, FS[2:0] is not equal to 000b or 001b.
4. It is highly recommended to connect an external pullup resistor and pull down resistor on
signals FS[2:0] and 24_48SEL_L to ensure that these signals achieve the desired logic level
and to determine the correct frequency selection under various loading and part leakage
conditions. The value for the external pull up resistor should be 10 k ohm and the value for the
external pull down resistor should be 1K ohm.
Chapter 3 Frequency Selections 11
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Table 2. Frequency Selections (Continued)
Input Configuration
Processor
(MHz)
PCI33 (MHz)
PCI33_HT66
(MHz)
24_48
(MHz)
14.318
(MHz)
Comment
FS2
FS1
FS0
PCI33_HT66
SEL_L
PCI
STOP33_L
24_48SEL_L
1 0 1 X 1 X 133 33 33 or
66
24 or
48
14.318 AMD Athlon™
processor
compatible
14 0 0 X 1 X 100 33 33 or
66
24 or
48
14.318 AMD Athlon
processor
compatible
0 1 1 X 1 X Reserved2
0 1 0 X 1 X Reserved2
0 0 1 1 1 X X1
input
(pin3
)
=X1 /
6
(pin3)
=X1 /
6
(pin3)
0 0 Bypass mode
for bring up and
mfgr test1
0 0 1 0 1 X X1
input
=X1 /
6
=X1 /
3
0 0 Bypass mode
for bring up and
mfgr test1
Notes:
1. During bypass mode the X1 input pin can be driven with an external clock signal from 10 MHz
to 100 MHz. This mode is used in system debug for frequency testing and is planned to be used
in the smart burn-in systems for the AMD64 processors used for production burn-in capability.
2. These operating modes are reserved for vendor specific test requirements and may be different
from vendor to vendor. These modes will not be used in the system.
3. In these cases, FS[2:0] is not equal to 000b or 001b.
4. It is highly recommended to connect an external pullup resistor and pull down resistor on
signals FS[2:0] and 24_48SEL_L to ensure that these signals achieve the desired logic level
and to determine the correct frequency selection under various loading and part leakage
conditions. The value for the external pull up resistor should be 10 k ohm and the value for the
external pull down resistor should be 1K ohm.
12 Frequency Selections Chapter 3
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Table 2. Frequency Selections (Continued)
Input Configuration
Processor
(MHz)
PCI33 (MHz)
PCI33_HT66
(MHz)
24_48
(MHz)
14.318
(MHz)
Comment
FS2
FS1
FS0
PCI33_HT66
SEL_L
PCI
STOP33_L
24_48SEL_L
0 0 0 X 1 X Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Tri-state mode
for board level
test
X X X 0 1 X 100,
133,
166 or
200
33 66 24 or
48
14.318 33 MHz vs. 66
MHz output
select3
X X X 1 1 X 100,133
, 166, or
200
33 33 24 or
48
14.318 33 MHz vs. 66
MHz output
select3
Notes:
1. During bypass mode the X1 input pin can be driven with an external clock signal from 10 MHz to
100 MHz. This mode is used in system debug for frequency testing and is planned to be used in the
smart burn-in systems for the AMD64 processors used for production burn-in capability.
2. These operating modes are reserved for vendor specific test requirements and may be different from
vendor to vendor. These modes will not be used in the system.
3. In these cases, FS[2:0] is not equal to 000b or 001b.
4. It is highly recommended to connect an external pullup resistor and pull down resistor on signals
FS[2:0] and 24_48SEL_L to ensure that these signals achieve the desired logic level and to
determine the correct frequency selection under various loading and part leakage conditions. The
value for the external pull up resistor should be 10 k ohm and the value for the external pull down
resistor should be 1K ohm.
Chapter 3 Frequency Selections 13
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Table 2. Frequency Selections (Continued)
Input Configuration
Processor
(MHz)
PCI33 (MHz)
PCI33_HT66
(MHz)
24_48
(MHz)
14.318
(MHz)
Comment
FS2
FS1
FS0
PCI33_HT66
SEL_L
PCI
STOP33_L
24_48SEL_L
X X X X 1 1 100,
133,
166 or
200
33 33 or
66
24 14.318 24 vs. 48 MHz
output select3
X X X X 1 0 100,
133,
166, or
200
33 33 or
66
48 14.318 24 vs. 48 MHz
output select3
X X X 0 0 X 100,
133,
166,
200
0 66 24 or
48
14.318 PCISTOP vs.
33 MHz and
66 MHz
selects3
Notes:
1. During bypass mode the X1 input pin can be driven with an external clock signal from 10 MHz to
100 MHz. This mode is used in system debug for frequency testing and is planned to be used in the
smart burn-in systems for the AMD64 processors used for production burn-in capability.
2. These operating modes are reserved for vendor specific test requirements and may be different from
vendor to vendor. These modes will not be used in the system.
3. In these cases, FS[2:0] is not equal to 000b or 001b.
4. It is highly recommended to connect an external pullup resistor and pull down resistor on signals
FS[2:0] and 24_48SEL_L to ensure that these signals achieve the desired logic level and to
determine the correct frequency selection under various loading and part leakage conditions. The
value for the external pull up resistor should be 10 k ohm and the value for the external pull down
resistor should be 1K ohm.
14 Frequency Selections Chapter 3
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Table 2. Frequency Selections (Continued)
Input Configuration
Processor
(MHz)
PCI33 (MHz)
PCI33_HT66
(MHz)
24_48
(MHz)
14.318
(MHz)
Comment
FS2
FS1
FS0
PCI33_HT66
SEL_L
PCI
STOP33_L
24_48SEL_L
X X X 0 1 X 100,
133,
166,
200
33 66 24 or
48
14.318 PCISTOP vs.
33 MHz and
66 MHz
selects3
X X X 1 0 X 100,
133,
166,
200
0 0 24 or
48
14.318 PCISTOP vs.
33 MHz and
66 MHz
selects3
X X X 1 1 X 100.
133,
166,
200
33 33 24 or
48
14/318 PCISTOP vs.
33 MHz and
66 MHz
selects3
Notes:
1. During bypass mode the X1 input pin can be driven with an external clock signal from 10 MHz to
100 MHz. This mode is used in system debug for frequency testing and is planned to be used in the
smart burn-in systems for the AMD64 processors used for production burn-in capability.
2. These operating modes are reserved for vendor specific test requirements and may be different from
vendor to vendor. These modes will not be used in the system.
3. In these cases, FS[2:0] is not equal to 000b or 001b.
4. It is highly recommended to connect an external pullup resistor and pull down resistor on signals
FS[2:0] and 24_48SEL_L to ensure that these signals achieve the desired logic level and to
determine the correct frequency selection under various loading and part leakage conditions. The
value for the external pull up resistor should be 10 k ohm and the value for the external pull down
resistor should be 1K ohm.
Chapter 3 Frequency Selections 15
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
16 Frequency Selections Chapter 3
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
18 Logic Block Diagram Chapter 4
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Chapter 5 Pin Locations and Descriptions
Table 3 contains the pin descriptions for the Clock Generator.
Table 3. Pin Locations and Descriptions
Name Pin No. of
Pins Type Pin Description
X1 3 1 I
Crystal Connection or External Reference:
Reference crystal input or external reference clock
input. This pin should include an internal 36-pF load
capacitance to eliminate the need for external load
capacitance.
X2 4 1 O Crystal Connection: Reference crystal feedback.
This output should include an internal 36-pF load
capacitance to eliminate the need for external load
capacitance.
CPUT[1:0] 41
37
2 O Processor Clock Outputs 1 and 0: Processor
push-pull “True” clock outputs of the differential pair.
Requires external termination.
CPUC[1:0] 40
36
2 O Processor Clock Outputs 1 and 0: Processor
push-pull “Complimentary” clock outputs of the
differential pair. Requires external termination.
PCI33_F 23 1 O 3.3V Free-Running PCI Clock Output: The
free-running PCI clock pin operates at 33-MHz. The
free-running PCI clock is not turned off when
PCISTOP33_L is activated Low.
PCI33[5:0] 13
14
17
18
21
22
6 O 3.3V PCI Clock Outputs: PCI clocks operate at 33
MHz.
PCI33_HT66[2:0] 7
8
11
3 O
3.3V PCI 33 MHz or HyperTransport™ Link
66 MHz Outputs: This group of outputs is selectable
between 33 MHz and 66 MHz based upon the state of
PCI33_HT66SEL_L. When running 66 MHz, these
outputs are for use as reference clocks to
HyperTransport technology-based devices.
Chapter 5 Pin Locations and Descriptions 19
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Table 3. Pin Locations and Descriptions (Continued)
Name Pin No. of
Pins Type Pin Description
PCI33_HT66SEL_L 6 1 I PCI33_HT66 MHz Select: This input selects the
output frequency of PCI33_HT66 outputs to either 33
MHz or 66 MHz. This input pin is dedicated to avoid
corruption of the input state due to PCI add-in cards
that may have termination resistors on the input
clocks. This input must have a weak (100K) internal
pullup resistor. This pin externally strapped low using
a 10 K ohm resistor to select if the 66 Mhz outputs are
desired. Low = 66 MHz outputs, High = 33 MHz
outputs
USB 31 1 O 3.3-V USB Clock Output: Fixed clock output at 48-
MHz.
24_48MHz/24
_48SEL_L
28 1 I/O 3.3-V Super I/O clock output: The Super I/O clock
may be strapped for 24-MHz or 48-MHz. This input
must have a weak (100K) internal pullup. This pin
will be externally strapped low using a 10 K ohm if
the 48 MHz output is desired. Low = 48 MHz output,
high = 24 MHz output
REF[0:2]/FS[0:2] 1
45
48
3 I/O 3.3V Reference Clock Outputs: Fixed clock output
at 14.318 MHz .
Frequency Select Inputs: Power-On strapping to set
device operating frequency as described in Table 2 on
page 11. These inputs must have weak (100 K)
internal pullup resistors. See Notes in Table 2 on page
11 for resistor strapping recommendation.
SPREAD 44 1 I Spread Spectrum Clocking Enable: Power-On
strapping that sets spread spectrum clocking as
enabled or disabled. This input allows the default
spread spectrum-clocking mode to be enabled or
disabled upon power up. This input must have a weak
(100K) internal pullup resistor. This pin is externally
strapped low using a 10 K ohm resistor if spread
disabled is desired. Low=disable, High=enable.
Note: all AMD Athlon™ processors and
AMD64 processor-based systems are
recommended for use with SSC, therefore the
default of this pin is enabled and should only be
turned off for debug and test purposes.
20 Pin Locations and Descriptions Chapter 5
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Table 3. Pin Locations and Descriptions (Continued)
Name Pin No. of
Pins Type Pin Description
PCISTOP33_L 24 1 I
Control for PCI33[0:5] and PCI33_HT66[0:2]
outputs operating at 33-MHz: Active-Low control
input to halt all 33-MHz PCI clocks except the free-
running clock. This input must have a weak internal
pullup resistor (100 K). Once this input has been
asserted, the PCI33 outputs and PCI33_HT66 outputs
operating at 33MHz must stop in the Low state
according to the timing diagram outlined in Section
1.6.2 on page 7 and must not violate the output duty
cycle requirements until stopped (no glitches or runt
cycles). Low = stop, High = running.
NC 12 1 Pin reserved for vendor specific features.
SDATA 26 1 I/O Data pin for I2C circuitry (SM Bus Rev1.0). This
input should have weak internal pullup resistor (100
K). In this case, no external pullup resistors would be
required. SDATA is a 5.0-V tolerant I/O.
Note Option: If CLK vendor only supports 3.3-V
tolerant I/O, they must provide an application
note in their spec on how to handle a 5V SMBus
(i.e., clamp circuit on the motherboard).
SCLK 25 1 I Clock pin for I2C circuitry (SM Bus Rev1.0). This
input must have weak internal pullup resistors (100K).
In this case, no external pullup resistors would be
required. SCLK must be a 3.3-V signal-tolerant I/O
but not 5.0-V tolerant..
VDD 2
9
16
19
29
35
38
46
8 P Power Connection: Connected to 3.3 V power
supply. Used to supply digital portions of the chip.
Chapter 5 Pin Locations and Descriptions 21
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Table 3. Pin Locations and Descriptions (Continued)
Name Pin No. of
Pins Type Pin Description
GND 5
10
15
20
27
30
34
39
47
9 G Power Connection: Connected directly to GND on
the motherboard. Used to ground digital portions of
the chip.
VDDA 43 1 P Analog VDD: Connected to 3.3-V power supply
through a filter on the motherboard. Used to supply
the main PLL on the chip.
GNDA 42 1 G Analog GND: Connected directly to GND on the
motherboard. Used to ground the main PLL on the
chip.
VDDF 32 1 P Analog VDD for 48-MHz PLL: Connected to 3.3-V
power supply through a filter on the motherboard.
Used to supply the 48-MHz PLL on the chip.
GNDF 33 1 G Analog GND for 48-MHz PLL: Connected directly
to GND on the motherboard. Used to ground the 48-
MHz PLL on the chip.
22 Pin Locations and Descriptions Chapter 5
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Chapter 6 Package Pinout – 48-Pin SSOP
The package pinout for a 48-pin SSOP package is defined to maximize performance. The package
pinout provides grouped VDD and GND pin pairs to maximize mutual coupling and to equalize
the distribution losses to each rail as seen at each signal location. The pinout includes dedicated
VDDA and GNDA signals to supply the variable PLL and VDDF and GNDF signals to supply the
fixed PLL. Figure 3 illustrates the SSOP package pinout.
Figure 3. SSOP Package Pinout
Chapter 6 Package Pinout – 48-Pin SSOP 23
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
24 Package Pinout – 48-Pin SSOP Chapter 6
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Chapter 7 Electrical Specifications
This chapter contains the electrical specifications for the clock generator.
7.1 Absolute Maximum Ratings
The absolute maximum ratings define the maximum non-operating conditions beyond which
predictable operation of the device might be impaired. The device should not be subjected to
conditions outside these ranges under any circumstances.
Table 4 describes the absolute maximum voltage, temperature, and ESD rating for the part.
Table 4. Absolute Maximum Ratings
Parameter Description Rating Unit
VDD, VDDA, VDDF Supply Voltage –0.5 to 3.8 V
VIN Input Voltage –0.5 to 3.8 V
TSTG Storage Temp –65 to +150 °C
ESD PROT Input ESD Protection
using Human Body
Model
>2 kV
7.2 Operating Conditions
Table 5 describes the normal operating conditions of the part.
Table 5. Operating Conditions
Parameter Description Min. Typical Max. Unit
VDD, VDDA, VDDF Analog and digital supply
voltages
3.135 3.465 V
TA Operating temperature,
ambient
0 70
°C
F(Input) Input frequency (crystal
or reference)
10 14.318 16 MHz
Chapter 7 Electrical Specifications 25
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
7.3 Electrical Characteristics
The electrical characteristics of the device define the electrical parameters and the ranges over
which the device must operate. These characteristics are grouped per input or output type. These
electrical characteristics must be maintained over the operating conditions shown in Table 5 on
page 25.
7.3.1 Logic Inputs
The logic input electrical characteristics are described in Table 6.
The input pins are PCI33_HT66SEL_L, FS[0:2], PCISTOP33_L.
Table 6. Logic Input Electrical Characteristics
Parameter Description Test Conditions Min. Typ. Max. Unit
VIL Input Low Voltage – GND-0.3 – 0.8 V
VIH Input High Voltage – 2.0 – VDD+0.3 V
IIL, IIH Input Low/High
Current
0 <Vin< VDD, Input
Leakage current
– –
±50 µA
7.3.2 SDATA, SCLK Input/Output
The SMBus electrical characteristics are described in Table 7.
Table 7. SDATA and SCLK Input Electrical Characteristics *
Parameter Description Test Conditions Min. Typ. Max. Unit
VIL Input Low Voltage – GND-0.3 – 0.8 V
VIH Input High Voltage – 2.0 – VDD+0.3 V
IIL, IIH Input Low/High
Current
0 <Vin< VDD,
Input Leakage
current
− – ±50 µA
VOL Output Low Voltage IOL = 1.75mA GND-0.3 – 0.4 V
IOL Output Low Current VO= 0.8V 2 – 50 mA
* Note: (5-V tolerant) If clock vendor only supports 3.3-V tolerant IO, they must provide an application
note in their specification on how to handle a 5-V SMBus (i.e., clamp circuit on the motherboard).
7.3.3 X1, X2 Crystal Input/Feedback
The crystal input electrical characteristics are described in Table 8.
26 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Table 8. Crystal Input/Feedback Electrical Characteristics
Parameter Description Test Conditions Min. Typ. Max. Unit
Cinx Crystal pin load capacitance – 27 36 45 pF
7.3.4 PCI/ HyperTransport™ Clock Outputs
The following PCI and HyperTransport™ clock output electrical characteristics are described in
Table 9.
The PCI and HyperTransport pins are PCI33[0:5], PCI_F , PCI33_HT66[0:2].
Table 9. PCI/HyperTransport™ Clock Output Electrical Characteristics
(Lump Capacitance Test Load =30 pF)
PCI33, PCI33_HT66
= 33MHz
PCI33_HT66 =
66MHz
Parameter Description Test Conditions Min Typ Max Min Typ Max Unit
VOL Output Low
Voltage
IOL = 9.0mA − – 0.4 − – 0.4 V
VOH Output High
Voltage
IOH = -12mA 2.4 – − 2.4 – − V
IOL Output Low
Current
VO= 0.8V 10 – − 10 – − mA
IOH Output High
Current
VO= 2.0V –15 – − –15 – − mA
DC
f Frequency,
Actual
– – 33.33 – – 66.6
67
MHz
tR Output Rise
Edge Rate
Measured from 20%
to 60%
1 – 4 1 – 4 V/ns
tF Output Fall
Edge Rate
Measured from 60%
to 20%
1 – 4 1 – 4 V/ns
AC
tD Duty Cycle Measured on rising
and falling edge at
1.5 V
45 – 55 45 – 55 %
Chapter 7 Electrical Specifications 27
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Table 9. PCI/HyperTransport™ Clock Output Electrical Characteristics
(Lump Capacitance Test Load =30 pF) (Continued)
PCI33,
PCI33_HT66 =
33MHz
PCI33_HT66 =
66MHz
Parameter Description Test Conditions Min Typ Max Min Typ Max Unit
tJC Jitter, Cycle-
to-Cycle
Measured on rising
edge at 1.5V.
Maximum difference
of cycle time between
two adjacent cycles.
0 – 250 0 – 250 ps
tJA Jitter,
Accumulated
Measured using the
JIT2 software package
with a Tek 7404
scope.
TIE (Time Interval
Error) measurement
technique:
Sample resolution =
50 ps,
Sample Duration = 10
µs
-1000 – 1000 -1000 – 1000 ps
tFS Frequency
Stabilization
from Power-up
(cold start)
Measured from full
supply voltage.
0 – 3 0 – 3 mS
AC
RON Output
Impedance
Average value during
switching transition.
Used for determining
series termination
value.
12 15 55 12 15 55 Ω
28 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
7.3.5 REF[2:0] Clock Outputs
The Reference clock output electrical characteristics are described in Table 10.
Table 10. Reference Clock Output Electrical Characteristics
(Lump Capacitance Test Load = 20 pF)
Parameter Description Test Conditions Min Typ Max Unit
VOL Output Low
Voltage
IOL = 9mA − – 0.4 V
VOH Output High
Voltage
IOH = -12mA 2.4 – − V
IOL Output Low
Current
VO= 0.8V 16 – − mA
DC
IOH Output High
Current
VO= 2.0V –22 – − mA
f Frequency, Actual Frequency generated by crystal
oscillator
14.318 MHz
tR Output Rise Edge
Rate
Measured from 20% to 80% 0.5 – 2 V/ns
tF Output Fall Edge
Rate
Measured from 80% to 20% 0.5 – 2 V/ns
tD Duty Cycle Measured on rising and falling edge
at 1.5V
45 – 55 %
tJC Jitter, Cycle-to-
Cycle
Measured on rising edge at 1.5V.
Maximum difference of cycle time
between two adjacent cycles.
0 500 1000 ps
tJA Jitter,
Accumulated
Measured using the JIT2 software
package with a Tek 7404 scope.
TIE (Time Interval Error)
measurement technique:
Sample resolution = 50 ps,
Sample Duration = 10 µs
–1000 – 1000 ps
tFS Frequency
Stabilization from
Power-up (cold
start)
Measured from full supply voltage. 0 – 3 ms
AC
RON Output Impedance Average value during switching
transition. Used for determining
series termination value.
20 24 60 Ω
Chapter 7 Electrical Specifications 29
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
7.3.6 USB, 24_48MHz Clock Outputs
The USB and 24_48MHz clock output electrical characteristics are described in Table 11.
Table 11. 24_48 MHz, USB Clock Output Electrical Characteristics
(Lump Capacitance Test Load = 20 pF)
24_48MHz USB, 24_48MHz
Parameter Description Test Conditions
Min Typ Max Min Typ Ma
x
Unit
VOL Output Low
Voltage
IOL = 9mA − 0.4
− 0.4 V
VOH Output High
Voltage
IOH = -12mA 2.4 − 2.4 − V
IOL Output Low
Current
VOL= 0.8V 16 − 16 − mA
DC
IOH Output High
Current
VOL= 2.0V -22 − –22 − mA
f Frequency,
Actual
Determined by PLL
divider ratio
24.004 48.008 MHz
tR Output Rise
Edge Rate
Measured from 20%
to 80%
0.5 2 0.5 2 V/ns
tF Output Fall
Edge Rate
Measured from 80%
to 20%
0.5 2 0.5 2 V/ns
tD Duty Cycle Measured on rising
and falling edge at
1.5V
45 55 45 55 %
tJC Jitter, Cycle-
to-Cycle for
24_48MHz
clock
Measured on rising
edge at 1.5V.
Maximum difference
of cycle time between
two adjacent cycles.
0 250 500 0 250 500 ps
AC
tJC Jitter, Cycle-
to-Cycle for
USB clock
(required for
USB2.0)
Measured on rising
edge at 1.5V.
Maximum difference
of cycle time between
two adjacent cycles.
0 200 ps
30 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Table 11. 24_48MHz, USB Clock Output Electrical Characteristics
(Lump Capacitance Test Load = 20 pF) (Continued)
24_48 MHz USB, 24_48 MHz
Parameter Description Test Conditions
Min Typ Max Min Typ Ma
x
Unit
tJA Jitter,
Accumulated
Measured using the
JIT2 software
package with a Tek
7404 scope.
TIE (Time Interval
Error) measurement
technique:
Sample resolution =
50 ps,
Sample Duration =
10 µs
–1000 1000 –1000 100
0
ps
tFS Frequency
Stabilization
from Power-
up (cold
start)
Measured from full
supply voltage
0 3 0 3 Ms
AC
RON Output
Impedance
Average value during
switching transition.
Used for determining
series termination
value.
20 24 60 20 24 60
Ω
Chapter 7 Electrical Specifications 31
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
7.3.7 CPUT[1:0], CPUC[1:0] Clock Outputs
The processor clock output electrical characteristics are described in Table 12.
Table 12. Processor Clock Output Electrical Characteristics
Parameter Description Test Conditions Min Typ Max Unit
tR Rise Edge Rate Measured at the AMD64 processors
test load. 0V± 400mV (differential
measurement)
2 – 10 V/ns
AC
tF Fall Edge Rate Measured at the AMD64 processors
test load 0V ± 400mV (differential
measurement)
2 – 10 V/ns
VDIFF Differential Voltage
(Single ended)
Measured at the AMD64 processors
test load
(single-ended measurement)
0.40 1.25 2.3 V
∆VDIFF Change in VDIFF_DC
Magnitude
Measured at the AMD64 processors
test load
(single-ended measurement)
–150 – +150 mV
VCM Common Mode
Voltage (Note 1)
Measured at the AMD64 processors
test load
(single-ended measurement)
1.05 1.25 1.45 V
∆VCM Change in Common
Mode Voltage
Measured at the AMD64 processors
test load
(single-ended measurement)
–200 – +200 mV
tD Duty Cycle Measured at the differential
crossing point
45 50 53 %
AC
tJC Jitter, Cycle-to-Cycle Measured at the differential
crossing point. Maximum
difference of cycle time between
two adjacent cycles.
0 100 200
ps
32 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Table 12. Processor Clock Output Electrical Characteristics (Continued)
Parameter Description Test Conditions Min Typ Max Unit
AC
tJA Jitter, Accumulated Measured using the JIT2 software
package with a Tek 7404 scope.
TIE (Time Interval Error)
measurement technique:
Sample resolution = 50psec,
Sample Duration = 10usec
–1000 1000 ps
t
FS Frequency
Stabilization from
Power-up (cold start)
Measured from full supply voltage 0 3 mS
R
ON Output Impedance Average value during switching
transition. Used for determining
series termination value. Note that
current mode drivers may have a
higher output impedance.
15 35 55
Ω
Figure 4 shows the single-ended measurement definitions referenced in Table 12.
Figure 4. Single-Ended Measurement Definitions
Chapter 7 Electrical Specifications 33
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
7.3.8 Differential Processor Clock Motherboard Termination Scheme
The processor clock motherboard termination scheme is comprised of 15 ohm series resistor
terminations located within 0.5” of clock generator, ~5” 100 ohm differential transmission line,
AC coupling caps and 169 ohm differential termination located <0.5” from the processor
CPUCLK pins.
The 100 ohm differential transmission lines are generated on the PCB using the stack-up and trace
spacing shown in Figure 5. The closest-neighboring signal must be at least 20 mils from the
CPUCLK differential pair to reduce motherboard crosstalk effects. The differential pair should be
routed with 25 mil length matching between the true and compliment signals. For best signal
integrity, these traces should be routed referenced to ground without crossing any plane splits.
A standard 4-layer motherboard stack-up is shown in Figure 5.
Figure 5. Four-Layer Motherboard Stack-Up and Impedance
34 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
The PCB stack-up parameters are outlined in Table 13.
Table 13. Board Stack-Up Parameters
Distance Size
H1 Dielectric Thickness = 4.7 mils, Dk = Dielectric constant =4.3 for FR-4
board material
H2 Middle Substrate layer ~ 50 mils
Th1 Signal Thickness = 0.5 oz copper (plated) ~2 mils
Th2 Power/Ground Plane Thickness = 1 oz copper (un-plated) ~ 1.4 mils
Wsig Signal trace width = 5 mils
Wdiff Spacing to differential Clk = 5 mils
Wadj Adjacent signal trace spacing = 20 mils
Figure 6 shows the motherboard processor clock termination scheme.
Figure 6. Motherboard Processor Clock Termination Scheme
7.3.9 Differential Processor Clock Input
The processor clock specifications assume the AMD64 processors contains a DC Bias generator
circuit to center the receiver inputs after the ac-coupling caps (3900 pF) to VDD/2 where VDD =
2.5 V ± 5%.
Figure 7 on page 36 shows target processor internal bias generation.
Chapter 7 Electrical Specifications 35
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Figure 7. Target Processor Internal Bias Generation
7.3.10 Differential Processor Clock for AMD64 Processors Test Load
The processor clock specification assumes the following test load:
• Fifteen ohm series resistor terminations (used to match the driver impedance with the board
impedance) located close to the clk generator
• Five inches of 100-ohm differential transmission line
• AC coupling caps (3900 pF) and 169 ohm differential termination located <0.5” from the
processor CPUclk pins
• Trace delay of 180 ps between the AC coupling caps and the processor bias generator—This is
to simulate the processor package trace propagation delay. Package trace impedance is 38
ohms single ended and 75 ohms differential.
Note: Equivalent package trace on FR-4 PCB is 12 mil trace/30mil space/12mil trace using
stackup as shown in Figure 6 on page 35.
• DC-bias generator circuit referenced to 2.5 V
• Five pF load cap
Figure 8 on page 37 shows the differential processor clock test load for the AMD64 processors.
36 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Figure 8. Differential Processor Clock for AMD64 Processors Test Load
7.4 Spread Spectrum
The spread spectrum characteristics are outlined in Table 14.
Table 14. Spread Spectrum Characteristics
Parameter Description Test Conditions Min Typ Max Unit
fSPREAD Spread spectrum at 33
kHz sweep rate1
– 0.0 –0.5 %
Note:
1. 33-KHz triangular modulation is required along with other spread amounts and modulation
algorithms, such as a maximum of 50 kHz
∆
f/
∆
t modulation, are left up to the clock generator
vendor to include as differentiating features.
7.5 Skew
Skew for AMD64 processor-based systems must be specified in two ways.
Time Independent Skew: The allowable skew between clock outputs that does not vary over
time (not dependent upon voltage or temperature changes or co-related with other outputs due to
voltage and temperature changes).
Time Variant Skew: The allowable skew between clock outputs that vary over time (with
changes in voltage and temperature and that does not effect processor, HT66, or PCI33 outputs
equally). The requirement for the time variant specification is derived directly from the
HyperTransport technology consortium source point.
Table 15 shows the skew characteristics for the AMD64 processor-based systems.
Chapter 7 Electrical Specifications 37
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Table 15. Skew Characteristics
Parameter Description Test Conditions Skew
5
Window
Unit
TSK_CPU_CPU Processor to processor skew,
time independent
Measured at crossing points
for CPUT rising edges.1
250 ps
TSK_CPU_PCI33 Processor to PCI skew, time
independent
Measured at crossing point
for CPUT rising edge and
1.5V for PCI clocks
500
(2000)3
ps
TSK_PCI33_PCI33 PCI33 to PCI33 clock skew,
time independent
Measured between rising at
1.5V
500 ps
TSK_PCI33_HT66 PCI33 to HT66 clock skew,
time independent
Measured between rising at
1.5V
500 ps
TSK_CPU_HT66 Processor to HT66 clock
skew, time independent
Measured at crossing point
for CPUT rising edge and
1.5 V for HyperTransport™
clocks
500
(2000)3
ps
Time Independent
TSK_HT66_HT66 HT66 to HT66 clock skew,
time independent
Measured between rising
edge at 1.5V
500 ps
Notes:
1. All skews in this skew budget are measured from the first referenced signal to the next (i.e.,
Tsk_CPU_PCI33 is the skew from the processor crossing point to any PCI33 rising edge @ 1.5V).
Therefore, this skew specifies the maximum skew window between these two signals to be 500 ps
whether the processor crossing leads or lags the PCI clock. This should not be interpreted to mean
that the PCI33 edge could either be 500 ps before the processor clock to 500 ps after the clock, thus
defining a 1000 ps window in which the PCI33 clock edge could fall.
2. Time variant and time invariant skews will add in real systems such that the worst-case skew
allowable is the sum of the two. All skew measurements should be taken at output pins of the clock
generator with SSC on.
3. If the Clock Vendor is only interested in supporting AMD64 processor-based systems (i.e., the clock
generator will not be used in K7 systems), the TSK CPU-PCI33 and TSK CPU-HT66 Time Independent skews
(as measured under nominal temperature and voltage) can be increased from 500 ps to 2000 ps. This
does NOT mean the total combined skew over temp/voltage is equal to 2000 ps + 500 ps=2500 ps.
The Time Variant skew of the clock generator must still remain <200 ps. The Time Variant skew
allows for skew changes induced by temperature and/or voltage variations.
4. The Time Variant specifications are derived from the HyperTransport Electrical Specification. The
Tclk2Rclkssc parameter can be ignored when the skew measurements are taken at the output of the
clock generator.
5. AMD recommends using an averaging function on the oscilloscope while taking skew measurements.
This technique has been shown to be effective in reducing jitter accumulation within the skew
measurements.
38 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
TSK_CPU_CPU Processor to processor skew,
time variant
Measured at crossing points
for CPUT rising edges.1
2002 ps
TSK_CPU_PCI33 Processor to PCI skew, time
variant
Measured at crossing point
for CPUT rising edge and
1.5 V for PCI clocks
2002 ps
TSK_PCI33_PCI33 PCI33 to PCI33 clock skew,
time variant
Measured between rising at
1.5 V
2002 ps
TSK_PCI33_HT66 PCI33 to HT66 clock skew,
time variant
Measured between rising at
1.5 V
2002 ps
TSK_CPU_HT66 Processor to HT66 clock
skew, time variant
Measured at crossing point
for CPUT rising edge and
1.5 V for HyperTransport™
clocks
2002 ps
Time Variant4
TSK_HT66_HT66 HT66 to HT66 clock skew,
time variant
Measured between rising
edge at 1.5 V
2002 ps
Notes:
1. All skews in this skew budget are measured from the first referenced signal to the next (i.e.,
Tsk_CPU_PCI33 is the skew from the processor crossing point to any PCI33 rising edge @ 1.5V).
Therefore, this skew specifies the maximum skew window between these two signals to be 500 ps
whether the processor crossing leads or lags the PCI clock. This should not be interpreted to mean
that the PCI33 edge could either be 500 ps before the processor clock to 500 ps after the clock, thus
defining a 1000 ps window in which the PCI33 clock edge could fall.
2. Time variant and time invariant skews will add in real systems such that the worst-case skew
allowable is the sum of the two. All skew measurements should be taken at output pins of the clock
generator with SSC on.
3. If the Clock Vendor is only interested in supporting AMD64 processor-based systems (i.e., the clock
generator will not be used in K7 systems), the TSK CPU-PCI33 and TSK CPU-HT66 Time Independent skews
(as measured under nominal temperature and voltage) can be increased from 500 ps to 2000 ps. This
does NOT mean the total combined skew over temp/voltage is equal to 2000 ps + 500 ps=2500 ps.
The Time Variant skew of the clock generator must still remain <200 ps. The Time Variant skew
allows for skew changes induced by temperature and/or voltage variations.
4. The Time Variant specifications are derived from the HyperTransport Electrical Specification. The
Tclk2Rclkssc parameter can be ignored when the skew measurements are taken at the output of the
clock generator.
5. AMD recommends using an averaging function on the oscilloscope while taking skew measurements.
This technique has been shown to be effective in reducing jitter accumulation within the skew
measurements.
Table 15. Skew Characteristics (Continued)
Parameter Description Test Conditions Skew
5
Window
Unit
Chapter 7 Electrical Specifications 39
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
40 Electrical Specifications Chapter 7
24707 Rev. 3.08 September 2003 Clock Generator Specification for AMD64 Processors
Chapter 8 SMBus Interface
The clock generator features an SMBus 1.0 connection that is designed for use in configuring
internal register settings that control particular device functions and read back the current state of
the control registers. Upon power-up, the clock generator initializes with default settings/board
strappings, therefore the use of the software programming is optional. In order to override the
initial settings, Byte0 bit0 must first be activated to allow for software settings. Once this bit is
set, the other registers can be programmed accordingly. Once a feature is changed, the value
programmed through the SMBus interface will override the initial hardware setting except where
noted. To return to the hardware strapped mode of operation, the software reads the strapped pin
states in Byte 4 and reprograms the device accordingly. Various clock generator manufacturers
may provide additional features as they see fit as long as this basic set of features are included.
8.1 SMBus Protocol
Simplifications to the SMBus 1.1 protocol specification have been made to define a minimum
supported feature set. The feature set is defined in this chapter.
8.1.1 Block Write
The byte/count/byte must be evaluated and compared to the number of received bytes to validate a
block write transfer. A miscompare must leave the register values unchanged. Other methods of
error notification are left to the vendor but none are expressly required.
Note: The block write compare is only required for server applications.
8.1.2 Block Read
The byte count byte is evaluated by the host controller and errors generated if the compare does
not match the transferred number of bytes. This error can result from
• Direct comparison of the byte count to transferred bytes
• The protocol error detected from the lack of a NACK condition in the case of an overrun
• The protocol error detected from the presence of a NACK condition when an ACK is expected
in the case of an under run
While the SMBus protocol requires host ACK bits to be sent to acknowledge each transferred
bytes, an implementation that ignores these ACK bits as a simplification is acceptable.
Clock generators that implement a simplified block read command, wherein the block read
command is not required and the R/W bit associated with the device address initiates a block read
are allowed in addition to but not as a substitution for the full SMbus block read protocol.
Chapter 8 SMBus Interface 41
Clock Generator Specification for AMD64 Processors 24707 Rev. 3.08 September 2003
Table 16 shows the I2C addresses.
Table 16. I2C Address
A6 A5 A4 A3 A2 A1 A0 R/W
1 1 0 1 0 0 1 -
Table 17 shows the register settings for frequency and spread spectrum control.
The Write enable and disable bits only take affect once the current block write has completed.
Table 17. Byte0: Frequency and Spread Spectrum Control Register
Bit Default Description
7 Inactive=0 Write Disable (write once). A 1 written to this bit, after a 1 has been written to
Byte 0 bit 0, will permanently disable modification of all configuration registers
until the part has been powered off. Once the clock generator has been Write
disabled, the SMBus controller should still accept and acknowledge subsequent
write cycles but it should not modify any of the registers.
6 Inactive=0 Spread Spectrum enable (0=disable, 1=enable). This bit provides a software
programmable control for spread spectrum clocking. The truth table for SSC is
as follows:
SPREAD pin, SSE bit, Enabled/Disabled
0, 0, Disabled
0, 1, Enabled
1, 0, Enabled
1, 1, Enabled
The readback version of this bit is the hardware strapped value such that the
software has the ability to know each state (either by readback or by writing the
SSE bit).
5 Inactive=0 FS4 (reserved for mapping to larger FS table through programmable FS bit only)
4 Inactive=0 FS3 (reserved for mapping to larger FS table through programmable FS bit only)
Note: FS[2:0] are the only required FS inputs and represent the only required operating states of the
device. FS[4:3] are defined and reserved so that implementations that provide a larger FS
table with additional operating states are enabled. None of these additional operating states
are required by the baseline feature set of the platforms that we envision, however, may serve
customer requirements or desires. When Byte 0 is read, the current state of the register should
be returned, not FS[2:0] or SPREAD pin states. These pin states are provided in Byte4.
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Table 17. Byte0: Frequency and Spread Spectrum Control Register (Continued)
Bit Default Description
3 Inactive=0 FS2 (corresponds to Table 2, on page 11)
2 Inactive=0 FS1 (corresponds to Table 2, on page 11)
1 Inactive=0 FS0 (corresponds to Table 2, on page 11)
0 Inactive=0 Write Enable. A 1 written to this bit after power up will enable modification of all
configuration registers and subsequent zeros written to this bit will disable
modification of all configurations except this single bit. Note that when a 1 has been
written to Byte0 bit 7 all modification is permanently disabled until the device power
cycles. Note also that block write transactions to the interface will complete,
however unless the interface has been previously unlocked, the writes will have no
effect. The effect of writing this bit does not take effect until the subsequent block
write command.
Note: FS[2:0] are the only required FS inputs and represent the only required operating states of the
device. FS[4:3] are defined and reserved so that implementations that provide a larger FS table
with additional operating states are enabled. None of these additional operating states are
required by the baseline feature set of the platforms that we envision, however, may serve customer
requirements or desires. When Byte 0 is read, the current state of the register should be returned,
not FS[2:0] or SPREAD pin states. These pin states are provided in Byte4.
The process of changing the FS bits thru software is as follows:
1. Upon powerup, Byte0, bits[5:1], and FS[4:0] are set to the default hardware settings.
2. A 1 is written to Byte0, bit0 to enable software control.
3. Every time Byte0 is written, the FIDs are affected.
4. If a 0 is written to Byte0, bit0 the software control is disabled. Disabling software control does
not cause the contents of Byte0 to default back to hardware setting for FS[4:0].
Table 18 outlines the register settings for the PCI clock control.
Table 18. Byte1: PCI Clock Control Register (1=Enabled, 0=Disabled)
Bit Default Description
7 Active=1 PCI33_HT66(1) enable (1=Enabled, 0=Disabled)
6 Active=1 PCI33_HT66(0) enable (1=Enabled, 0=Disabled)
5 Active=1 PCI33(5) enable (1=Enabled, 0=Disabled)
4 Active=1 PCI33(4) enable (1=Enabled, 0=Disabled)
3 Active=1 PCI33(3) enable (1=Enabled, 0=Disabled)
2 Active=1 PCI33(2) enable (1=Enabled, 0=Disabled)
1 Active=1 PCI33(1) enable (1=Enabled, 0=Disabled)
0 Active=1 PCI33(0) enable (1=Enabled, 0=Disabled)
Note: If a clock is set to free-running in Byte3and Byte 4, it can still be shut off using Byte1 or Byte2.
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Table 19 outlines the clock register settings available through SMBus.
Table 19. Byte2: PCI Clock, USB, 24_48MHz, REF[2:0] Control Register (1=Enabled,
0=Disabled)
Bit Default Description
7 Active=1 CPUT/C(1) shutdown. This bit can be used to disable the CPUT/C(1) clock
pair. During shutdown, CPUT = L and CPUC = H.
6 Active=1 CPUT/C(0) shutdown. This bit can be used to disable the CPUT/C(0) clock
pair. During shutdown, CPUT = L and CPUC = H.
5 Active=1 REF(2) enable (1=Enabled, 0=Disabled)
4 Active=1 REF(1) enable (1=Enabled, 0=Disabled)
3 Active=1 REF(0) enable (1=Enabled, 0=Disabled)
2 Active=1 24_48MHz enable (1=Enabled, 0=Disabled)
1 Active=1 USB enable (1=Enabled, 0=Disabled)
0 Active=1 PCI33_HT66(2) enable (1=Enabled, 0=Disabled)
The individual clock output enable/disable controls shown in Table 19 are intended to allow
unused clock outputs to be disabled to reduce electrical interference and electromagnetic radiation.
They are not intended to provide any dynamic control or power reduction features. Also, if a
clock is set to free running, it can still be shut off using Byte1 or Byte2.
Table 20 outlines the register control for PCI free running clocks.
Note: 1=Free running, 0=Controlled by PCISTOP.
Table 20. Byte3: PCI Clock Free Running Select Control Register
Bit Default Description
7 Inactive=0 Reserved for vendor specific functions
6 Inactive=0 Reserved for vendor specific functions
5 Inactive=0 PCI(5) free-running enable *
4 Inactive=0 PCI(4) free-running enable *
3 Inactive=0 PCI(3) free-running enable *
2 Inactive=0 PCI(2) free-running enable *
1 Inactive=0 PCI(1) free-running enable *
0 Inactive=0 PCI(0) free-running enable *
NOTE: * The individual free-running enable/disable controls are intended to allow individual
clock outputs to be made free running. A clock output that has its free-running bit
enabled will not be turned off with the assertion of either PCISTOP33_L or
PCISTOP66_L.
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Table 21 outlines some additional register settings for the clock control through SMBus.
Table 21. Byte4: Pin Latched/Real Time State (and One Free Running Control)
Bit Default Description
7 Active=1 PCI33_F output enable. This bit can be optionally used to disable the
PCI33_F output.
6 Active=1 SPREAD pin state
5 Active=1 24_48SEL_L pin power up latched state
4 Active=1 PCI33_HT66SEL_L pin state
3 Active=1 FS(2) power-up latched pin state
2 Active=1 FS(1) power-up latched pin state
1 Active=1 FS(0) power-up latched pin state
0 InActive=0 Reserved for vendor specific functions
Bits one through six of this register are intended to provide the original latch input pin state or the
current real time input pin state to software. These values can be used to return the clock
generator to its hardware configured operating state.
Table 22 outlines the register settings for clock vendor ID.
Table 22. Byte5: Clock Vendor ID
Bit Default Description
7 Varies Vendor ID, 001= reserved, 111=reserved
6 Vendor ID
5 Vendor ID
4 Device Revision ID
3 Device Revision ID
2 Device Revision ID
1 Device Revision ID
0 Device Revision ID
The 3-bit Vendor ID and 5-bit Device revision ID are intended to provide software with enough
information about the clock generator present in the system as to decide the correct configuration.
Vendor ID is assigned by AMD. The Device Revision ID is left to the clock generator vendor to
assign. The combination of the two provides a unique ID for software.
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Table 23. Byte6: Reserved for Byte Count
Bit Default Description
7 Reserved for device specific read byte count=MSB
6 Reserved
5 Reserved
4 Reserved
3 Reserved
2 Reserved
1 Reserved
0 Reserved
This register contains the number of bytes that the clock generator returns when issued a block
read command. It is defined and reserved such that additional bytes can be added as the clock
generator vendor sees fit. This register should contain the total number of bytes returned by a
block read command including vendor specific bytes above 6. Should a clock vendor wish to
provide test/debug mode registers above byte 6, this value can remain defaulted to 6 and later
updated through an SMBus write to allow access to these test/debug registers.
ATPG Function—This feature is only used during processor burn-in and is an optional feature
for the clock vendor to implement.
Two SMBus register bits are required to implement this feature:
• ATPG Mode Bit—Enables/Disables ATPG mode
• ATPG Pulse Bit—Triggers a single CPUclk pulse when set
Assuming that the clock synthesizer is operating either in Normal mode or PLL bypass mode, the
following sequence can be followed to generate an ATPG pulse.
• Set the Write Enable Bit (Byte/Bit 0) to program the Clock Synthesizer registers using the SM
Bus.
• Use the ATPG Mode Bit in the clock synthesizer configuration space to enable/disable the
ATPG mode. When this bit is set, the ATPG mode is enabled and the differential processor
clock outputs are pulled in differential low state (CPUT = 0 and CPUC = 1). The ATPG mode
also requires the USBclk (48MHz) to run as usual. All other clocks (PCI, Ref, PCI33_66,
SuperIO are not used by the ATPG mode therefore can either be left running or shut off.
• Use the ATPG pulse bit in the clock synthesizer program space to generate the ATPG pulse.
When the ATPG pulse bit is set, a differential ATPG pulse is generated on the differential
processor clock pins. The pulse width of the ATPG pulse is one processor clock period. The
processor clock period in the ATPG mode is same as the one in Normal mode or PLL bypass
mode.
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• Clear the ATPG pulse bit, since the clock synthesizer only recognizes 0 to 1 transition of the
ATPG pulse bit for next ATPG pulse generation.
• Use the ATPG pulse bit to generate the next ATPG pulse (set to 1).
• If the ATPG pulse bit is not set and the ATPG mode bit is cleared, then the synthesizer should
work in normal or PLL bypass mode.
Chapter 8 SMBus Interface 47
