Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!think.com!snorkelwacker.mit.edu!bu.edu!encore!maxzilla.encore.com!rnollman From: rnollman@maxzilla.encore.com (Richard Nollman) Newsgroups: comp.sys.ibm.pc.hardware Subject: 249 hours to generate Mandelbrot on my 286 Message-ID: <14705@encore.Encore.COM> Date: 2 May 91 12:54:13 GMT Sender: news@Encore.COM Reply-To: rnollman@maxzilla.encore.com (Richard Nollman) Distribution: usa Organization: Encore Computer Corp, Marlboro, MA Lines: 201 Nntp-Posting-Host: maxzilla.encore.com Thanks to everybody who responded to my 249 hours to generate MANDELBROT image on 286 posting. I thought I would post responses to date. I think I will take the unanimous advice and buy a coprocessor. My original posting is summarized in the first response. From rogerhef@matt.ksu.ksu.edu Wed May 1 14:17:02 1991 In comp.sys.ibm.pc.hardware you write: >Recently, using FRACTINT,I generated a Mandelbrot image on my 286 >clone that took 239 hours. I set the number of iterations to 1000 >(for those of you who are familiar with FRACTINT). The floating point >flag was turned on by FRACTINT and I do not have a math coprocessor. I >told a friend about it and he was puzzled. He has a 386 and the most >time a Mandelbrot image took to generate was about 14 hours and this >was deep into the set (billions magnification). I saved my image on >diskette and gave it to him. He generated the exact same image on his >computer in about 3 hours. We surmised that the cumulative effect of >many different factors accounted for the large difference in >calculation times. Given the differences in our machines (shown >below), does the time difference make sense? (We are trying to >determine if there is something in FRACTINT that may be configured >incorrectly on my machine). > my 286 his 386 > ------ ------- > 8 mghz 33 mghz > no cachex 64K cache > 16-bit I/O bus 32-bit I/O bus > no math coprocessor math coprocessor > 249 hours to 3 hours to calculate > calculate >Where should I best spend my money to upgrade (best bang for buck)? >Where am I losing the most processing speed? In FRACTINT with on my machine (386SX with a coprocessor) using floating point off, (integers only) it is about 2x as fast as with the coprocessor turned on. If you had a coprocessor it should speed up the calculations by 5-15 times, since this is flocting point intensive. Your friends machine is about 6 times faster than yours with no coprocessor. With his having a coprocessor it is about 60-100 times faster than yours on floating point. If you had a coprocessor it would put yours his machine only about 6-10 times faster. With floating point on the coprocessor it the big difference. If you run both programs with floating point off the difference will be considerably less extreame. -- Rogerhef@Matt.ksu.ksu.edu Roger Heflin EECE Grad Student (913) 532-5600 ************** From chao@CS.UCLA.EDU Wed May 1 14:30:08 1991 >Where should I best spend my money to upgrade (best bang for buck)? >Where am I losing the most processing speed? Math coprocessor. Get AMD287 for under $100. -- Chia-Chi Chao chao@cs.ucla.edu ..!ucbvax!cs.ucla.edu!cha ************** From SPG@ALPHA.SUNQUEST.COM Wed May 1 15:03:27 1991 OK, If one assumes that 33MHz is ~4 times faster than 8Mhz and that a 386 is >2 times faster than a 286 executing the same instructions at the same speed, then there's _still_ a factor of 10 hiding somewhere. A factor of 10 _is_ pretty likely if there's a lot of floating point math which can be offloaded to the co-processor. >Where should I best spend my money to upgrade (best bang for buck)? >Where am I losing the most processing speed? Off-hand I'd suggest a co-processor, but you probably won't see a 10 times decrease in run-time, because the co-processor for your machine will (most likely) be slower than your friend's. Go for a complete system upgrade... ;-) It might be worthwhile, If you're _really_ dedicating a machine to one task for 10 days straight. $0.02 Steve ************** From sp4@reef.cis.ufl.edu Wed May 1 18:20:22 1991 Those sound like reasonable numbers to me! His machine in just clock cycles is about 4 times as fast. The 386 is a bit faster than the 286, he has a cache, larger data bus, AND a coprocessor. The math coprocessor is probably the absolute biggest difference. If you wanted to generate fast Mandlebrot graphics the best investment would be the coprocessor! sp4@reef.cis.ufl.edu ************** From mark@typhoon.ucar.EDU Wed May 1 18:25:01 1991 > my 286 his 386 > ------ ------- > 8 mghz 33 mghz This is a big one. That's a factor of four right there -- that cuts the ~250 hours to ~60 hours. > no cachex 64K cache The cache basically allows the '386 to take full advantage of its clock speed. Not having one won't affect the '286 as much. > 16-bit I/O bus 32-bit I/O bus Not so much the I/O bus, but the register size, will affect things when you're in the realm where you're doing integer math. '386s, with their 32 bits, win here. The only I/O Fractint is doing is to the screen, and that *isn't* your limiting factor. > no math coprocessor math coprocessor This is another big one -- I imagine it could easily account for a factor of four to six in speed, accounting for the rest of the discrepancy. >Where should I best spend my money to upgrade (best bang for buck)? >Where am I losing the most processing speed? If you want to keep your current machine, a coprocessor would help a bunch. If you're planning on going to a '386, things will improve, though it'll cost more. (If you're rich, do both!) >Thanks. No sweat. -- -- Mark Bradford (bradfrd2@ncar.ucar.edu) <> To err is human, to moo bovine. "I'm not a squid, but I play one on the net." **************** From sstrazdu@hopi.intel.com Wed May 1 19:29:54 1991 Your numbers are worse than I would have expected, but they seem reasonable. For a program like Fractint a Math Coprocessor will make a HUGE difference. The program is spending almost all its time doing floating point calculations. If you want to run Fractint fast but a coprocessor, but if you want to run everything faster you will need to upgrade to a 386 or 486. Here's one more thing to think about. You're 286 with a 287 will probably run Fractint as fast as a 386SX with no coprocessor, but the 386SX will run most programs (those which don't use a lot of floating point) faster. **************** From kdorff@NMSU.Edu Thu May 2 02:37:04 1991 Don't feel so distraught. The problem is LACK OF COPROCESSOR. There was a fractint image that I created long ago, before I got a coprocessor, and these were the times: Image on 8mhz XT, no copper Image in 8mhz XT, copper 23 hours 18 minutes Same configuration, same machine, only difference was the coprocessor. Kevin *************** That last posting says it all. Thanks again. Rich Nollman