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System Address Map
4-8 Intel® 460GX Chipset Software Developer’s Manual
4.4 Legal and Illegal Address Disposition
Below is the disposition of addresses done by the Bus Interface Unit (BIU).
Table 4-1. Address Disposition
Address Range Outbound Inbound Dest. Decision
0-07FFFFh DRAM DRAM
080000h-09FFFFh DRAM DRAM MAR=11 or (Read and MAR= 01 and
no system bus LOCK#) or (Write and
MAR = 10)
PCI0a unclaimed MAR=00 or (Read and MAR=01 and
system bus LOCK#) or (Read and
MAR=10) or (Write and MAR=01)
0A0000h-0BFFFFh DRAM DRAM VGASE=0
PCIx unclaimed VGASE=1
0C0000h-0EFFFFh
(divided into 12 regions of 4k
bytes)
DRAM DRAM MAR=11 or (Read and MAR= 01 and
no LOCK#) or (Write and MAR = 10)
PCI0a unclaimed MAR=00 or (Read and MAR=01 and
LOCK#) or (Read and MAR=10) or
(Write and MAR=01)
0F_0000h-0F_FFFFh DRAM DRAM MAR=11 or (Read and MAR= 01 and
no LOCK#) or (Write and MAR = 10)
PCI0a unclaimed MAR=00 or (Read and MAR=01 and
LOCK#) or (Read and MAR=10) or
(Write and MAR=01)
10_0000h - PCIS[7] DRAM DRAM PXB uses LXGB instead of PCIS[7]
PCIS[7] - FDFF_FFFFh PCIx PCIx PCIS register determines target PCI
bus
On PCI if
MMBASE<=address<=MMT, then not
claimed. GXB: unclaimed
FE00_0000h-FE1F_FFFFh undefined undefined This region is reserved.
FE20_0000h-FE3F_FFFFh Expander port-
2 or PCI0A
Expander port
2 or PCI0A
If DEVNPRES[14]=0, send to
Expander port 2, else send to PCI-0a
FE40_0000h-FE5F_FFFFh undefined
undefined This region is reserved.
FE60_0000h to FEBF_FFFFh Config unit or
PCI-0a
Config unit or
PCI-0a
If <=8B then: if one of defined
registers read or write value, if not
then return all 1’s or terminate writes.
If >8B, then send to PCI-0a. NOTE:
Locks to this range are forbidden and
will hang the system
FEC0_0000 to FECF_FFFFh PCI x unclaimed SAR, IOABASE (PXB)
FED0_0000h to FEDF_FFFFh PCI 0a or
dropped
PXB will
forward IB and
mark it to
memory.
Reads are sent to PCI-0a for master
abort. Writes get No-Data response
and are dropped
FEE0_0000h to FEEF_FFFFh Interrupt
Transaction;
Reads sent to
PCI 0a, writes
dropped
interrupt for IB
write, PCI-0a
for read
Reads are sent to PCI-0a for master
abort. IB writes are turned to
interrupts. OB writes get No-Data
response and are dropped