Compaq 850 manual AGP Configuration, Config Reset Addr Register Value

Technical Reference Guide

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 (MCH, 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 4-6). Configuration is accomplished by BIOS during POST.

NOTE: Configuration of the AGP bus interface involves functions 0 and 1 of the MCH. Function 0 registers (listed in Table 3-4) include functions that affect basic control (GART) of the AGP.

Table 4-5.PCI/AGP Bridge Configuration Registers (MCH, Function 1)

Table 4-5.

PCI/AGP Bridge Function Configuration Registers

(MCH, Function 1)

PCI			PCI
Config.		Reset	Config.		Reset
Addr.	Register	Value	Addr.	Register	Value
00, 01h	Vendor ID	8086h	1Bh	Sec. Master Latency Timer	00h
02, 03h	Device ID	2532h	1Ch	I/O Base Address	F0h
04, 05h	Command	0000h	1Dh	I/O Limit Address	00h
06, 07h	Status	0020h	1E, 1Fh	Sec. PCI/PCI Status	02A0h
08h	Revision ID	00h	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	00h
1Ah	Subordinate Bus Number	00h	3F-FFh	Reserved	00h

NOTE:

Assume unmarked locations/gaps as reserved. Refer to Intel documentation for detailed register descriptions.

The AGP graphics adapter (actually its resident controller) is configured as a standard PCI device.

Compaq Deskpro EXS and Workstation 300 Personal Computers 4-13

Featuring the Intel Pentium 4 Processor

First Edition - December 2000