When copying large blocks of data on the Pentium Pro and Pentium II processors, you can
improve the speed of the copy by enabling the advanced features of the processor. In order to
use the special mode your data copy must meet the following criteria:
· The source and destination must be 8 byte aligned
· The copy direction must be ascending
· The length of the data must require greater than 64 repetitions
When all three of these criteria are true, programming a function using the rep movs and rep
stos instructions instead of a library function will allow the processor to perform a fast string
copy. Additionally, when your application spends a large amount of time copying you can
improve overall speed of your application by setting up your data to match these criteria.
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