Intel® 82854 Graphics Memory Controller Hub (GMCH)

4.7VGA I/O Mapped Registers

If Native Graphics mode is strapped, and Device #2 is enabled, and Function #0 within Device #2 is enabled for VGA, and IO_EN is set within Function #0 then GMCH claims a set of I/O registers for legacy VGA function. Table 17 lists direct CPU Access registers and Table 18 lists registers that are Index – Data registers that are used to access Internal VGA registers.

Table 17. VGA I/O Mapped Register List

Name

Function

Read @

Write @

 

 

 

 

ST00

VGA Input Status Register 0

3C2h

 

 

 

 

ST01

VGA Input Status Register 1

3BAh/3Dah

 

 

 

 

FCR

VGA Feature Control Register

3CAh

3BAh/3DAh

 

 

 

 

MSR

VGA Miscellaneous Status/Output Register

3CCh

3C2h

 

 

 

 

Table 18. Index – Data Registers

Name

Function

Index IO

Data IO

 

 

 

 

SRX

Sequencer Registers

3C4

3C5

 

 

 

 

GRX

Graphics Controller Registers

3CE

3CF

 

 

 

 

ARX

Attribute Control Registers

3C0

3C0: Write

 

 

 

3C1: Read

 

 

 

 

DACMASK

Pixel Data Mask Register

--

3C6h

 

 

 

 

DACSTATE

DAC State Register

--

3C7 Read Only

 

 

 

 

DACRX

Palette Read Index Register

3C7 Write Only

--

 

 

 

 

DACWX

Palette Write Index Register

3C8 Write Only

 

 

 

 

 

DACDATA

Palette Data Register

3C9

 

 

 

 

 

CRX

CRT Registers

3B4/3D4

3B5/3D5

 

 

(MDA/CGA)

(MDA/CGA)

 

 

 

 

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D15343-003

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Intel D15343-003 manual VGA I/O Mapped Registers, VGA I/O Mapped Register List, Index Data Registers