Implementation Note:

If the 64-byte region containing the addressed byte is not in the data cache, implementations are encouraged to allocate the region in the data cache without first reading it from memory. However, if any of the addressed bytes exist in the caches of other processors, they must be kept coherent with respect to those processors.

Processors with cache blocks smaller than 64 bytes are encouraged to implement WH64 as defined. However, they may instead implement the instruction by allocating a smaller aligned cache block for write access or by treating WH64 as a NOP.

Processors with cache blocks larger than 64 bytes are also encouraged to implement WH64 as defined. However, they may instead treat WH64 as a NOP.

4–146Alpha Architecture Handbook

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Compaq ECQD2KCTE manual Implementation Note