AMD-761 Datasheet, PDF (241/264 Pages) Advanced Micro Devices – AMD-761-TM System Controller Software/BIOS Design Guide

24081D—February 2002
Preliminary Information
AMD-761™ System Controller Software/BIOS Design Guide
Registers
-----
Bits
Description
0x0x0xB4h
AGP 4x Dynamic
Compensation
31:28 PVal
27:24
23
22
21:16
15:8
NVal
Reserved
DisStrb
Quantum_Cnt
Reserved
7
FW_Enable
6
4x_Override
5
Comp3.3
4:3
Reserved
2
PCI drive strength
1
Always_Compensate
0
Do_Compensate
Initialized/
Required
Value
Actual
Value
Key
fcn( )
Notes
yh
yh
0b
0b
000001b
00h
xb
xb
0b
0b
0b
xb
0b
c
P transistor strength, xfer
I/O pads
c
N transistor strength, xfer
I/O pad
r
A
1=Disable ADSTB[1:0}#
A
100-ms intervals for
Always_Compensate
r
0=Disable, 1=Enable
Controls 0x0x0xA4h[4] and
A B4/BF ^0x0x0xA8h[4]
Refer to “Feature Override
Bits for AGP Cards” on
page 208 for details.
0=Disabled,
1=Enabled -> Forces
0x0x0xA4h[0]->010b->2x AGP
A B4/BF _{Refer to “Feature Override}
Bits for AGP Cards” on
page 208 for details.
Do_Compensate=1 shows
A
PVal and NVal when Comp3.3
=1 with 3.3-V AGP cards
r
A
Normally = 0
0=Disable, 1=Enable
A B4/BB _{Refer to “AGP Interface” on}
page 205 for details.
Set to init dynamic
A
compensation
Clears when finished
KEY:
B= Mandatory BIOS function
A= AGP setup by BIOS
c = Calculated/set by AMD-761™ internal logic
P= Power management setup by BIOS o = Setup by OS or OS driver F = Performance enhancement set by BIOS
r = Hardcoded and reserved
u = PCI operational user interface E = Elective BIOS function
Chapter 7
Recommended BIOS Settings
229