Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uwm.edu!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!ncar!csn!kessner!david From: david@kessner.denver.co.us (David Kessner) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: 249 hours to generate MANDELBROT image on 286 Message-ID: <1991May3.050144.10280@kessner.denver.co.us> Date: 3 May 91 05:01:44 GMT References: <14697@encore.Encore.COM> <1991May2.124542.21865@engin.umich.edu> <1991May2.142752.23003@msuinfo.cl.msu.edu> Distribution: usa Organization: Kessner, Inc. Lines: 50 In article <1991May2.142752.23003@msuinfo.cl.msu.edu> draper@buster.cps.msu.edu (Patrick J Draper) writes: >Isn't there an option to use either integer or floating point math? If >so, a coprocessor wouldn't save you anything in the integer mode. > >The time gap is WAY too large here to be explained by clock speed or the >higher efficiency of a 386. As everyone knows, a 386 is only marginally >faster than a 286 at the same clock speed, running a 16bit system like >DOS. > >I'll bet that your friend's 386 is coonfigured for integer math, and the >286 machine is configured for floating point math. I have written integer code on the 386 that generates mandelbrot sets, and here are some of my observations: Integer code is less precise than floating point code but is two to three times faster than a 387. About the same as a Weitek. The biggest reason for this is the 386 has 32 bit registers which greatly speeds things up over the 286. Fractint uses the 32 bit registers. My Mandelbrot program used integers, but was otherwise BRUTE FORCE. It used no other optimizations, like edge detection. Still, it could genererate, on the average, an 800x600 picture at 2000 iterations in about 40 min! This is at varying levels of zoom but the number of iterations tells just how complex the image was. 320x200, 256 iteration pictures were done in less than 5 min. If the 286 was indeed using floating point math without a FPU, it could take days. Shift to integer and it will speed up by an order of magnatude. Don't bother with an FPU, it's a waste of money (if all you are doing is fractals). A CPU upgrade will have the biggest effect. The time given for the 386 is normal for floating point code-- but will be much faster when using integer math (Fractint is about as fast as my program). Mandelbrots is where the difference between the 286 and 386 is very evident. The biggest reason for this is the 32 bit registers for integer math, and the 32 bit data-bus for moving those floatig point numbers to and from RAM. When 32 bit registers are used, the 386 is three-four times faster than the 286 at the same clock speed (at least where Mandelbrots are concerned). >Patrick Draper "College is supposed to prepare you for the future, >cps.msu.edu but all my future's behind me." >draper@cps.msu.edu -- My GrandPa, age 85, Fall 1990 graduate -- 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);