Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!amdahl!pyramid!prls!mips!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: Maximum MIPS for a given memory bandwidth? Message-ID: <2406@winchester.mips.COM> Date: 16 Jun 88 04:13:18 GMT References: <6921@cit-vax.Caltech.Edu> <22050@amdcad.AMD.COM> <291@wombat.UUCP> <6955@cit-vax.Caltech.Edu> <5275@ecsvax.UUCP> Reply-To: mash@winchester.UUCP (John Mashey) Distribution: na Organization: MIPS Computer Systems, Sunnyvale, CA Lines: 35 In article <5275@ecsvax.UUCP> tpmsph@ecsvax.UUCP (Thomas P. Morris) writes: >As many or all of the readers of this group are well aware, what most >literature refers to as "MIPS" or "VAX MIPS" is not really a "MIP", >per se. Then the more enlightened literature points out that the >comparison is really to a mythical 1.0 "MIP" VAX 11/780. Why don't >we just refer to "VUPS", the term DEC coined an uses in their own >literature? (VAX 11/780 Unit Processor(S)) At least they are making >a nod at the apparent fact that a 780 is not `really' a 1 MIP machine... As noted before (some discussions are like boomerangs, they always come back): 1 VUP == 1 VAX 11/780, with VMS compilers. Note that some people also compare to MicroVAX II's (an MVUP!) which are slower than 780s, especially on floating point (be careful to compare apples with apples when looking at the Digital Review benchmarks, for example, which are often expressed as MVUP ratings). For DEC, VUPs work fine, because they compare CPUs in a family, using the same software. Thus, if the compilers optimize better over time, the processor ratios remain grossly constant per benchmark, and given that DEC uses a lot of benchmarks, I'd guess that compiler improvements that favor one model over another probably get washed out. When used elsewise, a VUP is a moving target, and if your compilers don't improve as fast as DEC's, your VUP-rating can diminish over time! As we've said many times, trying to boil even CPU performance down to 1 number is nonsense [for example, a "6-VUP" 8700 can be anywhere from 3-7X faster than a 780; other vendor's systems can very even more relative to the 780], but as much as you hate it, you get forced into it. argh. -- -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