Accelerated Graphics Port Interface Specification

AGP3.0 Interface Specification
Rev. 1.0
125
The Major and Minor Revision IDs in the NCAPID register are used to inform software of the register set
being implemented. Table 58 shows this relationship.
Table 58: Major/Minor Revisions
Major Revision Minor Revision Register Set Support
2h Don’t Care AGP2.0 Register Support
3h or greater 0h-4h AGP3.0 Core Specification Register Support
3h or greater 5h-9h AGP3.0 Appendix Specification Register Support
3h or greater Ah-Fh Reserved for future use
5.7 Register Table Format
Each Register is specified using the format below:
Table 59: Register Table
Bits Access Field Description
HighBit : LowBit
(Zero-origin)
<ACCESS> Name Description
Bit (Zero-origin) <ACCESS> Name Description
The ACCESS column is of the form:
[READ] – [WRITE] – [DEFAULT]
Table 60 defines the value of each sub-field:
Table 60: Sub-field Table
Field Value Meaning
[READ]
R Read Allowed
RZ Always Read-as-Zero
R1 Always Read-as-One
-- Read not allowed
[WRITE]
W Write Allowed
W1C Write of “1” clears bit to zero
IW Writes Ignored
MW Must Write back what is Read (Write-Under-Mask)
-- Write not allowed
[DEFAULT]
D’0 Power-on-Default is Zero
D’1 Power-on-Default is One
Dx Power-on-Default is not specified by AGP
D’?? Power-on-Default needs to be specified.