AMD-761 Datasheet, PDF (105/264 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
Bit Definitions (Continued)
AGP Compensation Bypass (Dev0:F0:0xB8)
Bit Name
Function
3–2 PSlewStrb
Slew Rate Control
This field is used to directly program the rise time in all AGP data strobes (AD_STB[1:0],
AD_STB[1:0]#). This field is not affected by the BYPStrb bit.
00 = Slew rate 0 (slowest)
01 = Slew rate 1
10 = Slew rate 2
11 = Slew rate 3 (fastest)
1–0 NSlewStrb
Slew Rate Control
This field is used to directly program the fall time in all AGP data strobes (AD_STB[1:0],
AD_STB[1:0]#). This field is not affected by the BYPStrb bit.
00 = Slew rate 0 (slowest)
01 = Slew rate 1
10 = Slew rate 2
11 = Slew rate 3 (fastest)
Programming Notes
There are three basic modes of bypass operation, as shown in the table below. Note that compensation applies to 1.5-V
signalling operation only.
Auto
Compensate
Non-strobe
Bypass
Strobes
All signals
All signals
Bypass Modes
Non-strobed signals auto-compensated while strobe signals programmed
manually in bypass mode.
All signals programmed manually in bypass mode.
All signals auto-compensated.
It is possible to configure the AGP I/O pads such that the non-strobed signals are auto-compensated while the strobes are
in bypass mode, but not vice-versa, as shown in the table above.
Once the non-strobed signals are programmed in bypass mode, these programmed bypassed values are also written to
the strobed signal I/O pads, until the strobed pads bypass values are also written.
Chapter 2
AMD-761™ System Controller Programmer’s Interface
93