RadiSys EPS-6315, Справочник по аппаратуре

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EPC
®
-6315 Hardware Reference
40
Cache Memory Regions:
A000–AFFF
B000–BFFF
Determines how the system deals with specified memory
blocks or shadow
1
memory. You can select one of these:
• Disabled (default) : The system does not cache memory.
• USWC Caching : System memory locations are not
cached (as with uncacheable memory) and coherency is
not enforced by the processor’s bus coherency protocol.
Speculative reads are allowed. Writes may be delayed
and combined in the write buffer to reduce memory
accesses.
Select this option for video frame buffers, where the write
order is unimportant as long as the writes update
memory so they can be seen on the graphics display.
• Write Back : Writes and reads to and from system
memory are cached, then written to system memory
when you perform a write-back operation.
Select this option to reduce bus traffic by eliminating
unnecessary writes to system memory.
This option provides the best performance, but requires
that all devices that access system memory on the system
bus be able to snoop memory accesses to ensure system
memory and cache coherency.
• Write Through : Writes and reads to and from system
memory are cached.
Select this option for frame buffers or when there are
devices on the system bus that access system memory,
but do not perform snooping of memory accesses.
• Write Protect : Reads come from cache lines when
possible, and read misses cause cache fills. Writes
propagate to the system bus and cause corresponding
cache lines on all processors on the bus to be
invalidated. Speculative reads are allowed.
When BIOS extensions are present in these regions,
enabling caching for that region increases performance
Field Description