
Register and Memory Mapping
6-4
82801AA and 82801AB Datasheet
6.2
I/O Map
The I/O map is divided into Fixed and Variable address ranges. Fixed ranges cannot be moved, but
in some cases can be disabled. Variable ranges can be moved and can also be disabled.
6.2.1
Fixed I/O Address Ranges
Table 6-3
shows the Fixed I/O decode ranges from the processor perspective. Note that for each
I/O range, there may be separate behavior for reads and writes. The hub interface cycles that go to
target ranges that are marked as “Reserved” will not be decoded by the ICH, and will be passed to
PCI. If a PCI master targets one of the fixed I/O target ranges, it will be positively decoded by the
ICH in Medium speed.
Refer to
Table A-2
for a complete list of all fixed I/O registers. Address ranges that are not listed or
marked “Reserved” are NOT decoded by the ICH (unless assigned to one of the variable ranges).
.
Table 6-3. Fixed I/O Ranges Decoded by ICH (Sheet 1 of 2)
I/O Address
Read Target
Write Target
Internal Unit
00h–08h
DMA Controller
DMA Controller
DMA
09h–0Eh
Reserved
DMA Controller
DMA
0Fh
DMA Controller
DMA Controller
DMA
10h–18h
DMA Controller
DMA Controller
DMA
19h–1Eh
Reserved
DMA Controller
DMA
1Fh
DMA Controller
DMA Controller
DMA
20h–21h
Interrupt Controller
Interrupt Controller
Interrupt
24h–25h
Interrupt Controller
Interrupt Controller
Interrupt
28h–29h
Interrupt Controller
Interrupt Controller
Interrupt
2Ch–2Dh
Interrupt Controller
Interrupt Controller
Interrupt
30h–31h
Interrupt Controller
Interrupt Controller
Interrupt
34h–35h
Interrupt Controller
Interrupt Controller
Interrupt
38h–39h
Interrupt Controller
Interrupt Controller
Interrupt
3Ch–3Dh
Interrupt Controller
Interrupt Controller
Interrupt
40h–42h
Timer/Counter
Timer/Counter
PIT (8254)
43h
Reserved
Timer/Counter
PIT
50h–52h
Timer/Counter
Timer/Counter
PIT
53h
Reserved
Timer/Counter
PIT
61h
NMI Controller
NMI Controller
Processor Interface
70h
Reserved
NMI and RTC Controller
RTC
71h
RTC Controller
RTC Controller
RTC
72h
RTC Controller
NMI and RTC Controller
RTC
73h
RTC Controller
RTC Controller
RTC
74h
RTC Controller
NMI and RTC Controller
RTC
75h
RTC Controller
RTC Controller
RTC
76h
RTC Controller
NMI and RTC Controller
RTC