6.1.4ICH Fixed I/O Registers

Port

Register Name

00h, 02h, 04h, 06h

Channel 0, 1, 2, 3 DMA Base & Current Address Regsiter

C0h, C4h, C8h, CCh

Channel 4, 5, 6, 7 DMA Base & Current Address Register

01h, 03h, 05h, 07h

Channel 0, 1, 2, 3 DMA Base & Current Count Register

C2h, C6h, Cah, CEh

Channel 4, 5, 6, 7 DMA Base & Current Count Register

10h-1Fh

Aliased at 00h-0Fh

20h

Master PIC ICW1 Init. Cmd Word 1 Register

 

Master PIC OCW2 Op Ctrl Word 2 Register

 

Master PIC OCW3 Op Ctrl Word 3 Register

21h

Master PIC ICW2 Init. Cmd Word 1 Register

 

Master PIC ICW3 Init. Cmd Word 1 Register

 

Master PIC ICW4 Init. Cmd Word 1 Register

 

Master PIC OCW1 Op Ctrl Word 3 Register

24h-25h, 28-29h,

Aliased at 20h-21h

2Ch-2Dh, 30h-31h,

 

34h-35h, 38h-39h,

 

3Ch-3Dh

 

40h

Counter 0 Interval Time Status Byte Format

 

Counter 0 Counter Access Port Register

41h

Counter 1 Interval Time Status Byte Format

 

Counter 1 Counter Access Port Register

42h

Counter 2 Interval Time Status Byte Format

 

Counter 2 Counter Access Port Register

43h

Timer Control Word Register

 

Timer Control Word Register Read Back

 

Counter Latch Command

50h-53h

Aliased at 40h-43h

61h

NMI Status and Control Register

70h

NMI Enable Register

 

Real-Time Clock (Standard RAM) Index Register

71h

Real-Time Clock (Standard RAM) Target Register

72h

Extended RAM Index Register

73h

Extended RAM Target Register

74h-75h

Aliased at 70h-71h

76h-77h

Aliased at 72h-73h or 70h-71h

81h, 82h, 83h

Channel 2, 3, 1 DMA Memory Low Page Register

84h-86h, 88h

Reserved Page Registers

89h, 8Ah, 8Bh

Channel 6, 7, 5 DMA Memory Low Page Register

8CH-8Eh

Reserved Page Registers

8Fh

Refresh Low Page Register

91h-9Fh

Aliased at 81h-8Fh

(except 92h)

 

92h

Fast A20 and INIT Register

continued

Compaq Deskpro EX and Deskpro EXS Series of Personal Computers 6-3

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Compaq EX Series, EXS Series manual ICH Fixed I/O Registers, Port Register Name