Chapter 7
Recommended BIOS Settings
229
24081D—February 2002
AMD-761™ System Controller Software/BIOS Design Guide
Preliminary Information
Registers
-----
Bits
Description
Initialized/
Required
Value
Actual
Value
Key
fcn( )
Notes
0x0x0xB4h
AGP 4x Dynamic
Compensation
31:28
PVal
yh
c
P transistor strength, xfer
I/O pads
27:24
NVal
yh
c
N transistor strength, xfer
I/O pad
23
Reserved
0b
r
22
DisStrb
0b
A
1=Disable ADSTB[1:0}#
21:16
Quantum_Cnt
000001b
A
100-ms intervals for
Always_Compensate
15:8
Reserved
00h
r
7
FW_Enable
xb
A
B4/BF
0=Disable, 1=Enable
Controls 0x0x0xA4h[4] and
0x0x0xA8h[4]
Refer to “Feature Override
6
4x_Override
xb
A
B4/BF
0=Disabled,
1=Enabled -> Forces
0x0x0xA4h[0]->010b->2x AGP
Refer to “Feature Override
5
Comp3.3
0b
A
Do_Compensate=1 shows
PVal and NVal when Comp3.3
=1 with 3.3-V AGP cards
4:3
Reserved
0b
r
2
PCI drive strength
0b
A
Normally = 0
1
Always_Compensate
xb
A
B4/BB
0=Disable, 1=Enable
Refer to “AGP Interface” on
page 205 for details.
0
Do_Compensate
0b
A
Set to init dynamic
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