Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!sdd.hp.com!caen!hellgate.utah.edu!csn!kessner!david From: david@kessner.denver.co.us (David Kessner) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: 249 hours to generate Mandelbrot on my 286 Message-ID: <1991May7.210057.3776@kessner.denver.co.us> Date: 7 May 91 21:00:57 GMT References: <1991May2.224345.434@cunixf.cc.columbia.edu> <3859@sixhub.UUCP> Organization: Kessner, Inc. Lines: 43 In article <3859@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes: >| 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. They are the same in one important respect: It uses the integer math part of the CPU rather than the floating point unit. While numerically they are different, as far as the CPU is concerned they are the same. >| 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. It's not a matter of telling fractint to use the FPU since it AUTOMATICALLY uses it if it is doing floating point and you have a FPU. There are too many variables as to why the 386 was faster, there's no one reason. Amung them: The difference in clock speed, the 386 registers, one used floating point, the other integer. > 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. I said it uses the 386's 32 bit registers. That's not to say that it REQUIRES a 386. It doesnt, but uses it's features if you do have one. >bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen) -- David Kessner - david@kessner.denver.co.us | do { 1135 Fairfax, Denver CO 80220 (303) 377-1801 (p.m.) | . . . If you cant flame MS-DOS, who can you flame? | } while( jones);