4 Feb
2007
4 Feb
'07
1 a.m.
Chuck Guzis wrote:
On 3 Feb 2007 at 22:38, Jim Leonard wrote:
Okay, just making sure. On 486, it was break-even; on Pentium, it was
indeed faster for most cases to pair instructions. (Although, if you
wanted to get fancy, you could copy memory even faster by loading 64
bits at a time into the FPU registers, then storing them out...)
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
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Could you clarify which 808x CPUs in particular
you're referencing in
the above? There isn't a single case from 808x to 486 where that code
will beat rep movsb. Were you referring to Pentiums and higher?
Just so--when x86 went superscalar, there was a significant
difference in the execution rate of V-pipe instructions as compared
to the more complicated CISC-type ones such as MOVSB. Which is also
why the DEC/JNZ turns out ot faster than the LOOP.