Chapter 2
AMD-761™ System Controller Programmer’s Interface
83
24081D—February 2002
AMD-761™ System Controller Software/BIOS Design Guide
Preliminary Information
Programming Notes
Bit Definitions
AGP Command (Dev0:F0:0xA8)
Bit
Name
Function
31–10
Reserved
Reserved
9
SBA_En
Sideband Addressing Enable
When this bit is set, sideband addressing is enabled.
8
AGP_En
AGP Operations Enable
When this bit is set, the AMD-761™ system controller accepts AGP operations. When this
bit is clear, the AMD-761 system controller ignores AGP operations.
7–6
Reserved
Reserved
5
R4G_En
4GB Address Indicator
This bit indicates that the AMD-761 system controller does not support addresses greater
than 4 Gbytes. The AMD-761 system controller supports only 32-bit addresses.
4
Fast_Writes
Fast Writes
0 = Fast writes disabled
1 = Fast writes enabled when the FW_Enable bit is also set in the AGP 4X Dynamic
Compensation register (Dev 0:F0:0xB4, bit 7)
3
Reserved
Reserved
2–0
Data_Transfer
_Mode
Data Transfer Mode
Only one bit must be set in this field to indicate the desired AGP data transfer rate.
001 = 1X AGP rate
010 = 2X AGP rate
100 = 4X AGP rate