Path: utzoo!utgpu!watserv1!watmath!att!att!pacbell.com!mips!zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!uunet!mcsun!ukc!dcl-cs!aber-cs!athene!pcg From: pcg@cs.aber.ac.uk (Piercarlo Grandi) Newsgroups: comp.arch Subject: SUN MMU design secrets Message-ID: Date: 4 Nov 90 18:15:54 GMT References: <1990Nov2.000650.18866@jarvis.csri.toronto.edu> <0093F1A8.A28E4920@KING.ENG.UMD.EDU> <1990Nov3.052952.1786@zoo.toronto.edu> <1990Nov3.150202.27353@ameristar> <1990Nov3.235958.21976@zoo.toronto.edu> Sender: pcg@aber-cs.UUCP Organization: Coleg Prifysgol Cymru Lines: 45 In-reply-to: henry@zoo.toronto.edu's message of 3 Nov 90 23:59:58 GMT X-Old-Subject: Re: processor for graphics terminal Henry Spencer observed: henry> ... Sun normally uses proprietary MMU designs that bear no henry> relation to (e.g.) the "Sparc Reference MMU". Worse, not only henry> are they proprietary but they are Top Secret, although apparently henry> Sun has entirely forgotten why, since they can't offer any henry> rational reason for it when asked. Uhm? I have copy of an article in the SUN magazine that gives virtually all the necessary details. A quick look at /usr/include/sun*/mmu.h will tell you all necessary details. Maybe not for the MMU, but SUN is famous for witholding other useful engineering details, and even MMU information has to be deduced, rather than read plainly in some document. On 3 Nov 90 23:59:58 GMT, henry@zoo.toronto.edu (Henry Spencer) said: henry> In article <1990Nov3.150202.27353@ameristar> rick@ameristar (Rick henry> Spanbauer) writes: rick> It may be a simple reason, like not wanting users to be able to rick> buy only SunOS tapes from Sun and then run the binaries on cheap rick> sparc clones, or to make the job of clone companies harder... Actually you *can* do that; people can license SunOS and offer it on their platforms. Also, people can provide a SunOS compatible ABI. Another simple reason may be to prevent people from implementing non SunOS operating systems on their hardware. But indeed if you try hard enough you can do it, as correctly observed: henry> I said "rational reason". The problem with the idea of keeping henry> it secret from the competition is that it's not that hard to henry> reverse-engineer the stuff if you try. [ ... ] This policy makes henry> life harder only for the legitimate customers. Another irrational reason, and one that is actually behind many corporate secrets (and military ones) is shame for a badly done job. In particular SUN MMUs have always been designed in a regrettable (when not outright unbelievable) way. -- Piercarlo "Peter" Grandi | ARPA: pcg%uk.ac.aber.cs@nsfnet-relay.ac.uk Dept of CS, UCW Aberystwyth | UUCP: ...!mcsun!ukc!aber-cs!pcg Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk