Xref: utzoo comp.misc:2426 comp.arch:4876 Path: utzoo!attcan!uunet!husc6!mailrus!nrl-cmf!ames!amdahl!pyramid!prls!mips!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.misc,comp.arch Subject: Re: Japanese 32-bit micro can be a 68020 or 80386 Message-ID: <2206@winchester.mips.COM> Date: 18 May 88 06:46:30 GMT References: <2006@sugar.UUCP> <53583@sun.uucp> Reply-To: mash@winchester.UUCP (John Mashey) Organization: MIPS Computer Systems, Sunnyvale, CA Lines: 41 In article <53583@sun.uucp> guy@gorodish.Sun.COM (Guy Harris) writes: >> Even the immediate implications are stunning, I think. One thing is that >> those of us who have always wanted to diddle microcode may soon be able to. >Well, maybe. An earlier article in "comp.arch" claimed: ... >I'm not sure that the "buckets of microcode" or, if you will, the "use the >microcode as a fast machine language and write a big interpreter in this >machine language" approach is necessarily the only way to get those languages >to run efficiently, or even necessarily the best way. >> Imagine a version of the microprogrammable chip in which the operating >> system could context switch among trusted sets of microprograms. Weird. >Weird, maybe, but did not the Burroughs 1700 series do this a long time ago? Yes, to handle support for different languages. Also, at least some of the XEROX D-machines were heavily microcoded; note that Smalltalk, for example, runs pretty well on 68020s + current RISCS. Robert F. Rosin once gave a great talk at Bell Labs (about 8-10 years ago), with a subject like "user-microcoding considered harmful", with a lot of history. He particularly described his experiences at SUNY waiting for the heavily-microcodable Nanodata QM-1 (like waiting for Godot), and what finally happened to them.....most ended up emulating PDP-11s running UNIX.... This is not to say that microcode is NECESSARILY bad; in many important machines it's been a useful emulation aid, and a useful design mechanism. On the other hand, these days, if you want to run multiple instruction sets: a) In the microprocessor domain, addin boards are awfully cheap. b) And even without extra hardware, fast processors can sometimes do fine job, via software techniques. Take a look at Insignia or Phoenix X86 emulation softwasre, for example. -- -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