Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!mips!winchester!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: machines with some loadable microcode are easier to fix Keywords: microcode hardware bugs Message-ID: <44473@mips.mips.COM> Date: 3 Jan 91 19:06:44 GMT References: <71537@bu.edu.bu.edu> Sender: news@mips.COM Reply-To: mash@mips.COM (John Mashey) Organization: MIPS Computer Systems, Inc. Lines: 33 In article <71537@bu.edu.bu.edu> gjc@buitc.bu.edu (George J. Carrette) writes: >A few months ago I posted to a couple news groups (not this one) a >program that crashed all RISC machines that it had been tried on, >but not the VAX and 68020 machines that I had tried it on. > >Much flaming resulted as expected, since I made the unfair statement >that the system vendors of RISC machines did significantly less >quality of testing than the vendors of CISC machines. > >There was also the unsupported statement that RISC machines, with >their rich set of "result is undefined" sequences of instructions were >more difficult to give a high quality of testing and/or engineering >proof of correctness. As a useful historical data point, as far as I can tell, UNIX (and other fair-sized OSs) managed to find problems in most chips / systems early in their life, problems that eluded diagnostics, and sometimes, even other versions of UNIX. Common problems usually are found around exception-handling, and they affected almost everything, CISC or RISC.... These include, at least: PDP-11/45 (in 1973), Moto 68K, NSC 32K, Intel X86, i860 (or so I'm told by reliable sources :-), and MIPS (we only had minor ones that could be worked around in software, but yes, we did find some. At least we didn't have any of the form "if an instruction with addressing mode A, is the last instruction on a page, and if it references a piece of data that spans page boundaries, and if the second part of the address misses, then Bad Things Happen." -- -john mashey DISCLAIMER: UUCP: mash@mips.com OR {ames,decwrl,prls,pyramid}!mips!mash DDD: 408-524-7015, 524-8253 or (main number) 408-720-1700 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086