82830MP Datasheet, PDF (56/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel® 830MP Chipset
R
4.5.1.15
GCC0 - GMCH Control Register #0 - Device #0
Address Offset:
Default Value:
Access:
Size:
50-51h
A072h
Read/Write, Read Only
16 bits
Bit
15
14:12
11
10
9
8
7
6:4
Descriptions
Reserved
Low Priority Grace Period. This value is loaded in SDRAM Arbiter when a request is ongoing and a higher
priority request is presented to the Arbiter. The arbiter continues to grant the first request for this specified
number of page hits (1KB). If the first requester causes a page miss or stops requesting the arbiter will
switch to the higher priority requester. (A request equals a Oct-word a.k.a dual-oct byte)
000 = 00
001 = 04
010 = 08 (Default)
011 = 16
100 = 24
101 = 32
110 = Reserved
111 = Reserved
Default Value=010.
Recommended Value without Internal Graphics = 011 → 16
Scratch Pad Enable. This bit when set to a “1”, allows the upper 256 Bytes of Device #0 RRBAR space
to be mapped to Scratch Pad Ram in the device. Once D_LCK is set, this bit becomes read only.
Note: The BIOS can use the scratch pad area when devices on the AGP bus are inactive (Not capable of
using the AGP Pipe or Side-Band command bus to issue read cycles to Main Memory).
Default Value=0.
Reserved.
Aperture Access Global Enable (R/W). This bit is used to prevent access to the aperture from any port
(CPU, PCI0 or AGP/PCI1) before the aperture range is established by the configuration software and
appropriate translation table in the main SDRAM has been initialized. It must be set after system is fully
configured for aperture accesses.
Default Value=0.
RRBAR Access Enable. This bit when set to a “1”, enables the RRBAR space. When “0”, accesses will
not decode to register range.
Default Value=0.
Reserved
IOQ request Grant Ceiling. This value is loaded in SDRAM Arbiter when an IOQ request is granted. It
provides a grant for the duration specified for as long as the request is active or until a fixed higher priority
request needs to be serviced.
111 = Infinite Ceiling (Default)
110 = 64
101 = 48
100 = 32
011 = 24
010 = 16
001 = 08
56
Datasheet
298338-001