Specifications

17 January 1997 – Subject to Change
System Address Mapping A–5
21164 Address Space Configuration Supported by the CIA
DMA access to system memory is achieved by means of windows through one of the
following three access methods:
•
The direct method uses the “Monster Window” with dual address cycles where
PCI address <33:0> equals memory address <33:0>.
•
The directly-mapped method concatenates an offset to a portion of the PCI
address.
•
The virtually-mapped method uses a scatter-gather translation map. The scatter-
gather map allows any 8KB page of PCI memory address region (page) to be
redirected to any 8KB cached memory page, as shown in Figure A–4.
Figure A–4 Address Mapping Overview
LJ04220A.AI5
21164 CPU
Cached Memory Space (8GB)
PCI Memory
Space
Scatter-Gather
Map
Direct Map
PCI Window
PCI Window
8KB
Page