ARM ARM926EJ-S Technical Reference Manual page 243

Write completion
Write-through (WT)
WT
ARM DDI0198D
The memory system indicates to the processor that a write has been completed at a point
in the transaction where the memory system is able to guarantee that the effect of the
write is visible to all processors in the system. This is not the case if the write is
associated with a memory synchronization primitive, or is to a Device or Strongly
Ordered region. In these cases the memory system might only indicate completion of
the write when the access has affected the state of the target, unless it is impossible to
distinguish between having the effect of the write visible and having the state of target
updated.
This stricter requirement for some types of memory ensures that any side-effects of the
memory access can be guaranteed by the processor to have taken place. You can use this
to prevent the starting of a subsequent operation in the program order until the
side-effects are visible.
In a write-through cache, data is written to main memory at the same time as the cache
is updated.
See Write-through.
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