Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!lll-lcc!pyramid!prls!mips!mash From: mash@mips.UUCP Newsgroups: comp.arch Subject: Re: Japanese 32-bit CPUs ( NEC V70 ) [really 29K] Message-ID: <377@winchester.UUCP> Date: Thu, 7-May-87 22:17:08 EDT Article-I.D.: winchest.377 Posted: Thu May 7 22:17:08 1987 Date-Received: Sat, 9-May-87 07:47:13 EDT References: <3810030@nucsrl.UUCP> <491@necis.UUCP> Reply-To: mash@winchester.UUCP (John Mashey) Organization: MIPS Computer Systems, Sunnyvale, CA Lines: 42 Keywords: V60, V70 In article <4070@necntc.NEC.COM> pec@necntc.UUCP (Paul Cohen) writes: >In article <372@winchester.UUCP> mash@winchester.UUCP (John Mashey) writes: >>In article <16561@amdcad.AMD.COM> bcase@amdcad.UUCP (Brian Case) writes: >>>In article <4016@necntc.NEC.COM> pec@necntc.UUCP (Paul Cohen) writes: > >>2 paths are usually better than one, as any chips will discover when they >>keep pushing clock rates. >I very much agree if you mean better performance. Do you also mean >better system cost? Depends; I was talking about performance, and actually, I meant separate I & D caches. >>If somebody says "20 addressing modes are good", to be convincing, they'd >>better be able to show tradeoffs, and show us the dynamic and static usages >>of those things, in real compiled code of substantial size. >A quibble here: Why is the size of the code important? All that I meant was: real programs, not toys, and not synthetic benchmarks. > >I wish that I had the time to do a study of the sort suggested (though >probably any results that I would get would be suspected of bias). >One question to ponder in this regard: suppose only 15 (or even only 5) >of the addressing modes were found to be extensively used by SOME compiler. >Could you conclude that you would be better off with only one or two >addressing modes? As usual, it depends. Maybe one discovers that no compilers use all of the modes, but all the modes are used substantially by something, or that the unused modes cost more to omit than include [by the time one has included the heavily-used ones.] THe point is that to show that "lots of modes" is a good thing, it is not sufficient to show one example of how a compiler might use them. What's really needed is a good tradeoff analysis: it's often hard, after the fact, to know what the modes cost in terms of cycle time. What can be measured is the usage frequency of the modes, and this is valuable information, and how we make progress in the architecture area. -- -john mashey DISCLAIMER: UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!mash, DDD: 408-720-1700, x253 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086