Path: utzoo!attcan!uunet!husc6!rutgers!apple!versatc!mips!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: MIPS/MFLOPS ratio Message-ID: <22737@winchester.mips.COM> Date: 5 Jul 89 06:31:49 GMT References: <596@megatek.UUCP> <749@maxim.erbe.se> Reply-To: mash@mips.COM (John Mashey) Organization: MIPS Computer Systems, Inc. Lines: 33 In article <749@maxim.erbe.se> rclaeson@erbe.se (Robert Claeson) writes: >In article <596@megatek.UUCP> mark@megatek.UUCP () writes: >>Lately, it seems that the integer performance of popularly available >>(especially RISC) computers seems to be outrunning the floating point >>performance. A little paper design for a SPARC system using the latest >>Cypress IU and FPC/FPU gets me a MIPS/MFLOPS ratio of about 10. >>This seems a little out of whack... it seems that older scientific >>processors had ratios in the 3-4 range. >A 17 MIPS Motorola 88100 RISC CPU has a fp performance of about 12 MFLOPS. >That gives (at least) me a MIPS/MFLOPS ratio for that chip of only ~1.4. Whenever I've seen MIPS/MFLOPS ratios discussed, I don't ever remember MFLOPS being peak-MFLOPS, but rather, LINPACK DP MFLOPS, usually FORTRAN, I think. Given the well-known fuzziness of mips-ratings, it's a little harder. If you take the currently-published numbers for a 20MHz 88K, they get 1.2MFLOPS FORTRAN DP LINPACK, and 2.2 Coded. If you use 17 MIPS, you're probably using Dhrystone-mips, which are usually 20-25% higher (assuming no strcpy inlining) that what people see for VAX-relative-versus-good-compilers-on-real-programs-mips. To get a bound, assume the LINPACK numbers shown, and 13-17 mips. This gives 13/2.2 = 6, and 17/1.2 = 14 as the limits of this. If I had to bet, as the compilers get better, I'd suspect a realistic number might be 14/2 = 7. All this is highly subject to cache configurations, etc , and so one must be verycareful not to over-interpret such numbers. -- -john mashey DISCLAIMER: UUCP: {ames,decwrl,prls,pyramid}!mips!mash OR mash@mips.com DDD: 408-991-0253 or 408-720-1700, x253 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086