845GL datasheet(69/193 Pages) INTEL

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Intel® 82845G/82845GL/82845GV GMCH Datasheet

3.5.1.24

ACAPID—AGP Capability Identifier Register (Device 0)

Address Offset:

A0–A3h

Default Value:

00200002h

Access:

Size:

32 bits

This register provides standard identifier for AGP capability.

3.5.1.25

AGPSTAT—AGP Status Register (Device 0)

Address Offset:

A4–A7h

Default Value:

1F000217h

Access:

Size:

32 bits

This register reports AGP device capability/status.

Bit

Description

31:24

Reserved.

23:20

Major AGP Revision Number (MAJREV).

These bits provide a major revision number of

Accelerated Graphics Port interface Specification, Revision 2.0

to which this version of GMCH

conforms. This field is hardwired to value of 0010b (i.e., implying Rev 2.0).

19:16

Minor AGP Revision Number (MINREV).

These bits provide a minor revision number of

Accelerated Graphics Port Interface Specification, Revision

2.0 to which this version of GMCH

conforms. This number is hardwired to value of 0000 which implies that the revision is 2.0. Together

with major revision number this field identifies the GMCH as an Accelerated Graphics Port Interface

Specification, Revision 2.0

compliant device.

15:8

Next Capability Poin.ter (NCAPTR):

AGP capability is the last capability described via the

capability pointer mechanism and therefore these bits are hardwired to 0 to indicate the end of the

capability linked list.

7:0

AGP Capability ID (CAPID).

This field identifies the linked list item as containing AGP registers.

This field has a value of 0000_0010b assigned by the PCI SIG.

Bit

Description

31:24

Request Queue (RQ).

This field is hardwired to 1Fh to indicate a maximum of 32 outstanding AGP

command requests can be handled by the GMCH. This field contains the maximum number of AGP

command requests the GMCH is configured to manage. Default =1Fh to allow a maximum of 32

outstanding AGP command requests.

23:10

Reserved.

Side Band Addressing Support (SBA).

This bit indicates that the GMCH supports side band

addressing. It is hardwired to 1.

8:6

Reserved.

Greater Than Four Gigabyte Support (GT4GIG).

This bit indicates that the GMCH does not

support addresses greater than 4 GB. It is hardwired to 0.

Fast Write Support (FW).

This bit indicates that the GMCH supports Fast Writes from the processor

to the AGP master. It is hardwired to a 1.

Reserved.

2:0

Data Rate Support (RATE).

After reset the GMCH reports its data transfer rate capability. Bit 0

identifies if the AGP device supports 1X data transfer mode, bit 1 identifies if AGP device supports

2X data transfer mode, bit 2 identifies if AGP device supports 4X data transfer

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