Specifications

A–32 System Address Mapping
Subject to Change – 17 January 1997
PCI-to-Physical Memory Addressing
Figure A–14 PCI DMA Addressing Example
Figure A–14 also shows that the CIA window can be larger than the corresponding
device’s DMA address range, as with device 0. Devices 1 and 2 have address ranges
that are accepted by one CIA window. Wn_BASE [Wn_BASE_SG] for each
window determines whether direct mapping or scatter-gather mapping is used to
access physical memory.
PCI single- and dual-address cycles have the following characteristics:
•
Dual-address cycle (DAC)—Issued only if <63:32> are nonzero in 64-bit PCI
address mode, and only if enabled by W3_BASE[DAC_ENABLE].
•
Single-address cycle (SAC)—All 32-bit addresses. A PCI device must use SAC
if bits <63:32> of a 64-bit address equal zero.
Figure A–15 shows the PCI window comparison logic.
LJ-04272.AI
21164 Memory
Space (8GB)
Scatter-Gather
Map
Direct
Map
PCI Device's DMA
Memory Space
PCI Memory
Space (4GB)
8KB
Page
PCI
Device 0
PCI
Device 1
PCI
Device 2
21164 System