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Intel® 460GX Chipset Software Developer’s Manual 4-5
System Address Map
4.2 I/O Address Map
The 460GX chipset allows I/O addresses to be mapped to resources supported on the I/O buses
underneath the 460GX chipset controller. This I/O space is partitioned into sixteen 4K byte
segments. Each of the segments can be individually configured to any I/O bus. Segment 0 is always
assigned to the compatibility I/O bus (of which there is only one per system).
There are four classes of I/O addresses that are specifically decoded by the 460GX chipset:
• All I/O addresses less than 100h: These addresses are specifically decoded as “defer-only”
addresses. The SAC does not post any I/O accesses to this range, regardless of the state of the
I/O posting enable bit. This is necessary because I/O accesses below 100h have historically
had ordering side effects: e.g. accesses to the 8259 Interrupt Masks.
Figure 4-2. Itanium™ Processor and Chipset-specific Memory Space
System
16 MB
FEC0_0000
FF00_0000
FE00_0000
12 MB
Chipset
4 MB
Specific
FFFF_FFFF
Chipset
Reserved
8 MB
I/O reserved
I/O SAPIC #0
I/O SAPIC #1
I/O SAPIC #2
I/O SAPIC #255
FEC0_0000
FEC0_1000
FEC0_2000
FECF_F000
FED0_0000
I/O SAPIC
#3 to # 254
FEFF_FFFF
2 MB
GART Table
2 MB
FEBF_FFFF
FE40_0000
FE20_0000
FE00_0000
FE60_0000
4KB each
FEC0_3000
PCI Bus 0A
PCI Bus 0B
PCI Bus 1A
PCI Bus 2A
PCI Bus mapping
of SAPIC addresses.
I/O reserved
Interrupt Delivery
On system bus - 1MB
1 MB
1 MB
FEF0_0000
FEE0_0000
Chipset
Reserved
Processor
Specific
Firmware