Accelerated Graphics Port Interface Specification

AGP3.0 Interface Specification
Rev. 1.0
46
2.7.3 NCAPID: AGP IDENTIFIER REGISTER
Offset: CAPPTR
Size: 4 bytes
MAJOR AND MINOR REVISION ID NUMBER
Table 25: Major/Minor Revisions
Bits Access Field Description
31:24 RZ-IW Reserved Always returns 0 on read; write operations have no effect.
23:20 R-IW-
D’0011
MAJOR Major revision number of AGP3.0 interface specification this
device conforms to. A Value of 3h or greater indicates
AGP3.0.
19:16 R-IW-
D’0000
MINOR Minor revision number of AGP3.0 interface specification this
device conforms to. Range for minor revision for Core
Specification registers is 0h-4h. First release will use 0h.
15:8 R-IW-Dx NEXT_PTR Pointer to next item in Capabilities List. Must be NULL for
final item in list.
7:0 R-IW-
D’CAPID
Value
CAP_ID The value of this field is determined as follows:
Location of Registers CAPID Value
AGP Target Host to PCI
Bridge
00000010
AGP Target PCI-to-PCI
Bridge
New ID
AGP Master 00000010
The Major/Minor Revision fields are used to determine register set support by a given target or
master. The Minor Revision field is split between Core Specification base features support and
Appendix features support. When the AGP configuration registers are located in the host bridge,
the CAP_ID remains the same as AGP to maintain backward compatibility with legacy software.
A new CAPID is assigned for registers located in a P2P bridge.
The Major and Minor Revision IDs in the NCAPID register are used to inform software of the
register set being implemented. Table 26 shows this relationship:
Table 26: Major and Minor Revision ID Selection
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
The NEXT_PTR field contains a pointer to the next item in the list. The NEXT_PTR field in a final list item must
contain a NULL pointer.