Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!cornell!batcomputer!pyramid!prls!mips!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: Harvard Architecure Message-ID: <1904@winchester.mips.COM> Date: 19 Mar 88 21:41:30 GMT References: <8803011911.AA06922@decwrl.dec.com> <3460011@hpsrla.HP.COM> <1071@PT.CS.CMU.EDU> <7614@apple.Apple.Com> <2594@pdn.UUCP> Reply-To: mash@winchester.UUCP (John Mashey) Organization: MIPS Computer Systems, Sunnyvale, CA Lines: 33 In article <2594@pdn.UUCP> alan@pdn.UUCP (0000-Alan Lovejoy) writes: >The 68020 **CONSISTENTLY** benchmarks twice as fast with the instruction >cache turned on (compared to its being turned off). Apparently the >'030 gets **AT LEAST** a 30% performance boost from turning on the data >cache (so I have been told by those who have benchmarked one). > >Enough said. 1) Even small I-caches are almost always useful: the question that started this all was whether or not small D-caches were useful, and if so, how much, and under what circumstances. 2)One would expect (rightly or wrongly) that overall system design would heavily influence the benefit level of a small on-chip D-cache. I.e., one would expect that, for example, turning the D-cache on would help more in a Sun-3/160 - style design (no external cache) than in a /260 design (well-designed, fast external cache). (Expectations could be wrong, but...) 3) Data would help: whenever 68030 systems become widely available, and especially if there are convenient ways to turn the caches on/off, people could do comp.arch a large service by: a) running large, realistic benchmarks b) reporting the results c) reporting the clock speed and overall memory system configuration. Until then, all we've got to go on is indirect reports, having no idea what sorts of benchmarks and configurations are being tested. Alan: can you possibly offer more fo the details, or is it still proprietary? -- -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