Chapter 3: BIOS configuration
35
Cache Base 0–512k
Cache Base 512–
640k
Determines how the system caches base memory in the
specified area:
You can select one of these:
•
Write Back (default)
: 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 are
propagated to the system bus and cause corresponding
cache lines on all processors on the bus to be
invalidated. Speculative reads are allowed.
•
uncached
: The system does not cache memory.
Cache Extended
Memory Area
Determines how the system caches extended memory. You
can select one of these:
•
Write Back (default)
: 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 are
propagated to the system bus and cause corresponding
cache lines on all processors on the bus to be
invalidated. Speculative reads are allowed.
•
uncached
: The system does not cache memory.
Field
Description
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