Agp Configuration - Compaq Deskpro EP 6233 Technical Reference Manual

Chapter 4 System Support
4.3.2

AGP CONFIGURATION

AGP bus operations require the configuration of certain parameters involving system memory
access by the AGP graphics adapter. The AGP bus interface is configured as a PCI device
integrated within the north bridge (82443, device 1) component. The AGP function is, from the
PCI bus perspective, treated essentially as a PCI/PCI bridge and configured through PCI
configuration registers (Table 4-7). Configuration is accomplished by BIOS during POST.
NOTE: Configuration of the AGP bus interface involves functions 0 and 1 of the
82443. Function 0 registers (listed in Table 3-6) include functions that affect basic
control (GART) of the AGP.
Table 4–7. PCI/AGP Bridge Configuration Registers (82371, Function 1)
PCI Config.
Addr. Register
00, 01h Vendor ID
02, 03h Device ID
04, 05h Command
06, 07h Status
08h Revision ID
0A, 0Bh Class Code
0Eh Header Type
18h Primary Bus Number
19h Secondary Bus Number
1Ah Subordinate Bus Number
NOTE:
Assume unmarked locations/gaps as reserved. Refer to Intel documentation for detailed
register descriptions.
[1] 7181h for 443EX, 7191h for 443BX
[2] 03h for 443EX, 00h for 443BX
4-14 Compaq Deskpro EP Series of Personal Computers
Table 4-8.
PCI/AGP Bridge Function Configuration Registers
(82443EX/BX, Function 1)
Reset
Value
8086h
[1]
0000h
0220h
[2]
0406h
01h
00h
00h
00h
First Edition - April 1998
PCI Config.
Addr. Register
1Bh Sec. Master Latency Timer
1Ch I/O Base Address
1Dh I/O Limit Address
1E, 1Fh Sec. PCI/PCI Status
20, 21h Memory Base Address
22, 23h Memory Limit Address
24, 25h Prefetch Mem. Base Addr.
26, 27h Prefetch Mem. Limit Addr.
3Eh PCI/PCI Bridge Control
3F-FFh Reserved
Reset
Value
00h
F0h
00h
02A0h
FFF0h
0000h
FFF0h
0000h
80h
00h