In causal consistency, it is permitted that concurrent writes be seen in a different order on different machines, although causally related ones must be seen in the same order by all machines. The next step in relaxing memory is to drop the latter requirement. Doing so gives PRAM consistency, which is subject to the condition:

Writes done by a single process are received by all other processes in the order in which they were issued, but writes from different processes may be seen in a different order by different processes.

PRAM consistency is due to Lipton and Sandberg. PRAM stands for Pipelined RAM, because writes by a single process can be pipelined, that is, the process does not have to stall waiting for each one to complete before starting the next one.

                    
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