Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!sixhub!davidsen
From: davidsen@sixhub.UUCP (Wm E. Davidsen Jr)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: 249 hours to generate Mandelbrot on my 286
Message-ID: <3859@sixhub.UUCP>
Date: 7 May 91 01:15:20 GMT
References: <1991May2.224345.434@cunixf.cc.columbia.edu>
Reply-To: davidsen@sixhub.UUCP (bill davidsen)
Organization: *IX Public Access UNIX, Schenectady NY
Lines: 43

In article <1991May2.224345.434@cunixf.cc.columbia.edu> brian@cunixf.cc.columbia.edu (Brian Hoffman) writes:
| I can't believe that 30 hosers responded to your question about Fractint
| and not a single one (as far as I can tell) got it right.

  Sorry, they were about right, you are wrong on this one.

| Your question was basically this:  why is fractint much faster on a 33-386
| than on my 12-286.
| 
| The lame answer was this:  get a math coprocessor.

  Yes. as the originally posting very carefully noted, FRACTINT turned
on the float flag, as it should when it runs out of bits for the fixed point
math it uses when it can.

| In general, fractint runs faster on a 386 because it was written that way.
| A math coprocessor will NOT help because fractint uses integer math.

  This is correct, in many cases f.p. won't help. However, it does not
use integer math, it uses fixed point. Not the same, as a numerical
analyst to explain.

| However, it is possible to tell fractint to use a math coprocessor, and this
| will indeed speed up calculations on your 286.  But this was not the source
| of the discrepancy you noticed originally.

  I'm pretty sure you're wrong on this one, too. The early versions ran
faster on a 286 in fixed point mode, but it depends on what's being
done.

  Someonbe said that recent versions of fractint use the 386 32 bit
stuff, not correct, the original program was called something like
fract386, and ONLY ran on a 386. Later emulation was added.

  My advice: a 386SX-20 board for about $600 with memory, and a Cyrix
387SX for about $220. Worlds faster, particularly on the stuff which
*doesn't* use the 387. I really suggest the Cyrix, it's up to 2x faster
than Intel, cheaper, and lower power.
-- 
bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
    sysop *IX BBS and Public Access UNIX
    moderator of comp.binaries.ibm.pc and 80386 mailing list
"Stupidity, like virtue, is its own reward" -me