Chapter 4 System Support
Compaq Deskpro EP Series of Personal Computers
First Edition - April 1998
4-14
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)
Table 4-8.
PCI/AGP Bridge Function Configuration Registers
(82443EX/BX, Function 1)
PCI Config.
Addr. Register
Reset
Value
PCI Config.
Addr. Register
Reset
Value
00, 01h Vendor ID 8086h 1Bh Sec. Master Latency Timer 00h
02, 03h Device ID [1] 1Ch I/O Base Address F0h
04, 05h Command 0000h 1Dh I/O Limit Address 00h
06, 07h Status 0220h 1E, 1Fh Sec. PCI/PCI Status 02A0h
08h Revision ID [2] 20, 21h Memory Base Address FFF0h
0A, 0Bh Class Code 0406h 22, 23h Memory Limit Address 0000h
0Eh Header Type 01h 24, 25h Prefetch Mem. Base Addr. FFF0h
18h Primary Bus Number 00h 26, 27h Prefetch Mem. Limit Addr. 0000h
19h Secondary Bus Number 00h 3Eh PCI/PCI Bridge Control 80h
1Ah Subordinate Bus Number 00h 3F-FFh Reserved 00h
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
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