Write Buffer - ARM ARM926EJ-S Technical Reference Manual

Caches and Write Buffer
4.2

Write buffer

4-4
The write buffer is used for all writes to a noncachable, bufferable region, write-through
region, and write misses to a write-back region. A separate buffer is incorporated in the
DCache for holding write-back data for cache line evictions or cleaning of dirty cache
lines.
The main write buffer has a 16-word data buffer and a four-address buffer.
The DCache write-back buffer has eight data word entries and a single address entry.
The MCR drain write buffer instruction enables both write buffers to be drained under
software control.
The MCR wait for interrupt causes both write buffers to be drained and the
ARM926EJ-S processor to be put into a low-power state until an interrupt occurs.
Write buffer behavior is described in Table 4-4 on page 4-6.
No forwarding takes place for read accesses which have corresponding pending writes
in the write buffer. For such accesses the write buffer is drained and the value fetched
from external memory.
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