AMD-761 Datasheet, PDF (102/264 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
Bit Definitions (Continued)
AGP 4X Dynamic Compensation (Dev0:F0:0xB4)
Bit Name
Function
1 Always_
Compensate
Always Compensate
When set, dynamic compensation is performed by AGP on an ongoing basis at
regular intervals.
0 Do_Compensate Do Compensate
This bit is used to initiate a dynamic compensation command on AGP. This bit is cleared by
the AMD-761™ system controller when the compensation cycle is complete. See the
programming note below on recommendation for exiting bypass mode.
Programming Notes
When transitioning from bypass enabled to disabled via the AGP Compensation Bypass register (Dev 0:F0:0xB8), the
Do_Compensate bit should be set. AGP should not be subsequently enabled until the Do_Compensate bit is read back as
a 0, indicating that the compensation cycle is complete.
Refer to the AGP Compensation Bypass register (Dev 0:F0:0xB8) for details of bypass mode.
Table 9. I/O Pad Drive Strength and Input Type
BYPASS TYPEDET#
PCI
0
0
X
0
1
0
0
1
1
1
X
X
BYPASS TYPEDET#
PCI
X
0
X
X
0
X
X
1
X
X
1
X
AGP Mode
N/A
N/A
N/A
N/A
AGP Mode
4X
1X/2X
1X/2X
1X/2X
Output Drive Strength
Compensated Strength
AGP-1X Strength
PCI Strength
Bypass, User Configurable
Input Type
Differential
Single-Ended
Single-Ended
Single-Ended
90
AMD-761™ System Controller Programmer’s Interface
Chapter 2