AMD-761 Datasheet, PDF (244/264 Pages) Advanced Micro Devices – AMD-761-TM System Controller Software/BIOS Design Guide

Preliminary Information
AMD-761™ System Controller Software/BIOS Design Guide
24081D—February 2002
7.1.2
Examples: AGP Compensation Register Settings (0xB4-0xBB)
TYPEDET#
0x0x0x88[25]
Type_Det = 1 indicates that a card in the AGP slot is a 3.3-V
signalling card, which supports 2X AGP maximum. A 3.3-V
signalling card cannot run above 2X AGP.
Type_Det = 0 indicates that a card in the AGP slot is a 1.5-V
signalling card, which supports 4X AGP maximum. A 1.5-V
signalling card can run at 1X, 2X, or 4X AGP rates.
Refer to “AGP Interface” on page 205 for details on how the
value of the Type_Det bit and the settings of the AGP
compensation register affect the settings in AGP
Compensation Bypass register.
0x0x0x..
Type_Det = 1 2X AGP Maximum Type_Det =1 == 3.3-V card in AGP slot
B4h B5h B6h B7h B8h B9h BAh BBh No Option
48h 00h 01h C5h 0Fh FFh 0Fh C5h
0x0x0x..
Type_Det = 0 4X AGP Maximum, Reduced to 2X AGP with 4X_Override
B4h B5h B6h B7h B8h B9h BAh BBh Option 1
4Ah 00h 01h D8h 8Fh FFh 04h D8h 4x_Override and Always_Compensate
0x0x0x.. B4h B5h B6h B7h B8h B9h BAh BBh Option 2
48h 00h 01h D8h 8Fh FFh 84h D8h ^{4x_Override and Bypass}
0x0x0x..
Type_Det = 0 4xAGP Maximum, Options of Always Compensate, Bypass and Fast Writes
B4h B5h B6h B7h B8h B9h BAh BBh Option 1
02h 00h 01h D8h 8Fh FFh 04h D8h ^{Always_Compensate}
0x0x0x.. B4h B5h B6h B7h B8h B9h BAh BBh Option 2
82h 00h 01h D8h 8Fh FFh 04h D8h ^{Always Compensate and Fast Writes}
0x0x0x.. B4h B5h B6h B7h B8h B9h BAh BBh Option 3
00h 00h 01h D8h 8Fh FFh 84h D8h ^Bypass
0x0x0x.. B4h B5h B6h B7h B8h B9h BAh BBh Option 4
80h 00h 01h D8h 8Fh FFh 84h D8h Bypass and Fast Writes
232
Recommended BIOS Settings
Chapter 7