> > means the performance of using a soft modem is about 8 Pentium MHz,
> > on the grounds that 1 32-bit Pentium MHz =~ 1 64-bit R4000 MHz in the
>
> Way off. Firstly Im dubious about the 8Mhz, secondly the R4K's tend to
> have DSP instructions (ones that are useful). Pentiums dont have an
> add/multiply with no stall instruction once per clock.
An unrolled multiply accumulate _can_ be done in 2 clocks per argument on
a Pentium, however (hint: the fxchg instruction can be made to take 0(!!)
clocks if ordered properly). I put together a signal processing app that
did dot products at 45 mflops on a P90 last year. But this was only if its
working set fit within the L1 cache.
With MMX, a 16-bit fixed point multiply accumulate could probably be done
with about about a cycle per operand (multiply, shift, add, exchange)
provided your vectors could be into four chunks large enough to unroll
nicely.
-- "Love the dolphins," she advised him. "Write by W.A.S.T.E.."
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