Re: Pentiums and EU
Hawke writes:
> Rob, does ex.exe take advantage of extra features
> found in 486/586 processors that aren't found
> in 386's?
Yes. When I compile it with WATCOM C, I choose
C compiler options that produce the fastest possible
code for a Pentium, but do not use any instructions
that don't exist on a 386/486.
For example, a Pentium has two instruction pipelines,
so it can potentially execute 2 machine instructions at the same
time in parallel (superscalar) provided there are no dependencies
between the instructions, such as one instruction needs the result
of the previous instruction. There's an option to reorder machine
instructions to make this more likely. That option will speed
up the code on a Pentium, but won't hurt performance on a
386 or 486. For the older processors the order doesn't matter
(usually).
As an other example, on a Pentium, 8-byte floating-point
numbers load faster to/from memory if they are aligned
on an 8-byte boundary in memory. For a 386/486 it doesn't
matter, 4-byte alignment is enough. So Euphoria
aligns f.p. numbers on 8-byte boundaries.
In general, most Pentium-specific optimizations are
unlikely to hurt performance on the older processors. It's not
worth it to have separate versions optimized specifically for
a 386 or a 486. You might only gain 1% at best.
Regards,
Rob Craig
Rapid Deployment Software
http://members.aol.com/FilesEu/
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