82801CA Datasheet, PDF (149/521 Pages) Intel Corporation – I/O Controller Hub 3-S (ICH3-S)

Functional Description
Operating Systems (e.g., Windows* 98, Windows* 2000 and Windows NT*) reprogram the system
timer; hence, will not run into this problem.
For some other OSs (e.g., DOS), the BIOS should restore the timer back to 54.6 ms before passing
control to the OS. If the BIOS is entering ALT access mode before entering the suspend state it is
not necessary to restore the timer contents after the exit from ALT access mode.
5.12.10.1 Write Only Registers with Read Paths in ALT Access Mode
The registers described in the following table have read paths in ALT access mode. The access
number field in the table indicates which register will be returned per access to that port.
Table 5-46. Write Only Registers with Read Paths in ALT Access Mode
Restore Data
Restore Data
I/O
Addr
# of
Rds
Access
Data
I/O
Addr
# of
Rds
Access
Data
00h 2
01h 2
02h 2
03h 2
04h 2
05h 2
06h 2
07h 2
1
DMA Chan 0 base
address low byte
2
DMA Chan 0 base
address high byte
1
DMA Chan 0 base count
low byte
2
DMA Chan 0 base count
high byte
40h
7
1
DMA Chan 1 base
address low byte
2
DMA Chan 1 base
address high byte
1
DMA Chan 1 base count
low byte
2
DMA Chan 1 base count
high byte
41h
1
1
DMA Chan 2 base
address low byte
42h 1
2
DMA Chan 2 base
address high byte
70h 1
1
DMA Chan 2 base count
low byte
C4h 2
2
DMA Chan 2 base count
high byte
1
DMA Chan 3 base
address low byte
2
DMA Chan 3 base
address high byte
C6h 2
1
DMA Chan 3 base count
low byte
C8h 2
2
DMA Chan 3 base count
high byte
1
Timer Counter 0 status,
bits [5:0]
2
Timer Counter 0 base count
low byte
3
Timer Counter 0 base count
high byte
4
Timer Counter 1 base count
low byte
5
Timer Counter 1 base count
high byte
6
Timer Counter 2 base count
low byte
7
Timer Counter 2 base count
high byte
Timer Counter 1 status,
bits [5:0]
Timer Counter 2 status,
bits [5:0]
Bit 7 = NMI Enable,
Bits [6:0] = RTC Address
1
DMA Chan 5 base address low
byte
2
DMA Chan 5 base address
high byte
1
DMA Chan 5 base count low
byte
2
DMA Chan 5 base count high
byte
1
DMA Chan 6 base address low
byte
2
DMA Chan 6 base address
high byte
Intel^® 82801CA ICH3-S Datasheet
149