Intel D15343-003 GMC Gmch Miscellaneous Control Register Device #0, Rrbar Access Enable-R/W, Vga

Models: D15343-003

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Intel® 82854 Graphics Memory Controller Hub (GMCH)

4.8.13GMC – GMCH Miscellaneous Control Register (Device #0)

Address Offset:

50-51h

Default Value:

0000h

Access:

 

Read/Write

Size:

 

16 bits

 

 

Bit

Descriptions

 

 

 

15:10

Reserved

 

 

 

 

9

Reserved

 

 

 

8

RRBAR Access Enable—R/W:

 

1: Enables the RRBAR space.

 

0: Disable

 

 

 

 

7:1

Reserved

 

 

 

0

MDA Present (MDAP)—R/W:

 

This bit should not be set when the VGA Enable bit is not set. If the VGA enable bit is set, then

 

accesses to IO address range x3BCh–x3BFh are forwarded to Hub interface. If the VGA enable bit

 

is not set then accesses to IO address range x3BCh–x3BFh are treated just like any other IO

 

accesses. MDA resources are defined as the following:

 

Memory: 0B0000h – 0B7FFFh

 

I/O: 3B4h, 3B5h, 3B8h, 3B9h, 3BAh, 3BFh,

 

(including ISA address aliases, A[15:10] are not used in decode)

 

Any I/O reference that includes the I/O locations listed above, or their aliases, will be forwarded to

 

Hub interface even if the reference includes I/O locations not listed above.

 

The following table shows the behavior for all combinations of MDA and VGA:

 

VGA

MDA Behavior

 

0 0

All References to MDA and VGA go to Hub interface (Default)

 

0 1

Reserved

 

1 0

All References to VGA go to PCI.

 

 

MDA-only references (I/O address 3BF and aliases will go to Hub interface.

 

1 1

VGA References go to PCI; MDA References go to Hub interface

 

 

 

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D15343-003

Page 58
Image 58
Intel D15343-003 GMC Gmch Miscellaneous Control Register Device #0, Rrbar Access Enable-R/W, MDA Present MDAP-R/W, Vga