Mail Archives: djgpp/1997/01/09/18:09:17
Orlando Andico wrote:
> > First: floating point is slower at add and subtracts. If all you ever do
> > is add/sub then integer will be 2* faster *at least*. If you use
> > Divides are slightly faster in fpu but a lot less hassle than fixed
> > point. If you use single precision fpu mode they are always 2* faster.
> > Also its possible to continue issuing integer instructions while a float
> > divide executes. That allows tricks like performing a perspective divide
> > in effectively 1 clk.
> is this true for 486's? or just Pentiums? i'm hacking at some MPEG audio
For 486's, try to avoid floating-point. The integer math will be much
faster, though you still could do some long floating-point operations at
the same time as a bunch of integer calculations. Also, on a 486,
multiplies (and especially divides) will always be slow unless you fake
it.
> code (MAPLAY -- UNIX-based really) so that it can run faster on 486's (the
> generic MAPLAY chokes on anything less than a Pentium-60) and I would love
> to learn about quickie speedups of FP code.
Look on my web page if you want opcode/timing listings for 486/Pentiums.
-- Yamaha / XYZZ "May farce the with be you."
mailto:scriven AT CS DOT ColoState DOT edu
mailto:scriven AT VIS DOT ColoState DOT edu
http://www.vis.colostate.edu/~scriven/
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