Specifications

17 January 1997 – Subject to Change
System Address Mapping A–17
21164 Address Space
Figure A–9 PCI Memory Sparse Space Address Generation (Region 3)
The 21164 microprocessor provides six physical address bits <39:34> that can be
used to backfill the “lost” sparse space bits. However, other 21164 platforms use
these high-order bits in different ways, encoding multiple PCI ports for instance.
Therefore, for easier software portability, these bits are not used.
A.3.3 PCI Sparse I/O Space
PCI sparse I/O space has characteristics similar to the PCI sparse memory space. PCI
sparse I/O space is located in the address range 85.8000.0000 to 85.FFFF.FFFF. This
2GB 21164 address segment maps to two 32MB regions of PCI I/O address space. A
read or write transaction to this space causes a PCI I/O read or write transaction.
The high-order PCI address bits for region A are handled as follows:
•
This region has addr<34:30> equal to 10110
2
, and addresses the lower 32MB of
PCI sparse I/O space; thus, ad<31:25> are set to zero by the hardware (see
Figure A–10).
•
ad<24:3> are derived from addr<29:8>.
•
This region is used for ISA addressing (the ISA 64KB I/O space cannot be
relocated).
•
ad<2:0> are defined in Table A–5.
SBZ
PCI Address
4 3
Length in Bytes
Byte Offset
HAE_MEM CSR
PCI QW Address
LJ-04267.AI
1
1
21164 Address
0 0
21164
int4_valid
31 02 01 00
34 33 05 04 03 02 00
39 38
35
060708
31 07
03
32 31
26 25
08 01 0002
30
010