Posted writing is subject to criticisms. Although the memory interface is unused when the posted write starts, that does not mean that it will not be needed for a read operation before the posted write is completed. In that case, the CPU may be stalled for a few cycles until the posted write is completed. Posted writing also makes overall operation more complex since the posted write buffer(s) add one more place which must be handled properly to maintain cache/memory coherency.
Actual improvements from Posted writing are difficult to estimate analytically and no figures are available on measured improvement. It is probably not large in most cases.
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