AMD-761 datasheet(88/264 Pages) AMD

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AMD-761™ System Controller Programmer’s Interface

Chapter 2

AMD-761™ System Controller Software/BIOS Design Guide

24081D—February 2002

Preliminary Information

Programming Notes

Bypass_PLLs

Bypass PLLs

This bit is set for test and debug of the AMD-761™ system controller with the internal

PLLs disabled.

0 = AMD-761 system controller PLLs enabled

1 = AMD-761 system controller PLLs bypassed; clocks driven from SYSCLK and AGPCLK

pins directly to internal clock trees

Dis_Divider

Disable Divider

For internal test only.

11–8

Reserved

SIP_ROM_En

SIP ROM Enabled

This bit indicates that the external SIP ROM is enabled and is read to create the SIP stream

to the AMD Athlon processor, instead of the internally generated SIP table.

6GP_Strap

General-Purpose Strap

This bit may be used as a general-purpose strap for communicating motherboard- specific

information to BIOS. The AMD-761 system controller does not use this strap internally.

5In_Clk_En

INCLK Enable

This bit indicates that the AMD-761 system controller delays the INCLK to the AMD Athlon

processor. When reset, the motherboard is expected to provide delay in the etch to center

the INCLK with the data.

Out_Clk_En

OUTCLK Enable

This bit indicates that the AMD Athlon processor delays the OUTCLK to the AMD-761

system controller. When reset, the motherboard is expected to provide delay in the etch to

center the OUTCLK with the data.

3–0

CPU0_Divider

CPU Divider

This bit field contains the CPU clock multiplier field supplied by the processor. Together

with the Clk_Speed field and the S2K0_Bus_Len field, these fields allow the AMD-761

system controller to properly program the AMD Athlon™ processor system bus

initialization logic using the SIP protocol.

The clock multiplier field is also known as the Frequency Identification (FID) bits and the

values are shown below.

Bit Definitions (Continued)

Config Status (Dev0:F0:0x88)

Bit

Name

Function

FID Value Multiplier FID Value Multiplier FID Value Multiplier FID Value Multiplier

0000

11.0

0100

5.0

1000

7.0

1100

9.0

0001

11.5

0101

5.5

1001

7.5

1101

9.5

0010

12.0

0110

6.0

1010

8.0

1110

10.0

0011

12.5

0111

6.5

1011

8.5

1111

10.5

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