Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!bonnie.concordia.ca!ccu.umanitoba.ca!herald.usask.ca!alberta!aunro!aupair.cs.athabascau.ca!atha!decwrl!uunet!mcsun!ukc!dcl-cs!aber-cs!athene!pcg From: pcg@test.aber.ac.uk (Piercarlo Antonio Grandi) Newsgroups: comp.arch Subject: Re: Translating 64-bit addresses Message-ID: Date: 13 Mar 91 14:45:42 GMT References: <6590@hplabsz.HP.COM> <12030@pt.cs.cmu.edu> <6626@hplabsz.HP.COM> <92-9BOB@xds13.ferranti.com> <5R+9C=A@xds13.ferranti.com> Sender: aro@aber-cs.UUCP Organization: Coleg Prifysgol Cymru Lines: 35 Nntp-Posting-Host: aberdb In-reply-to: peter@ficc.ferranti.com's message of 12 Mar 91 14:52:17 GMT On 12 Mar 91 14:52:17 GMT, peter@ficc.ferranti.com (Peter da Silva) said: peter> In article peter> pcg@cs.aber.ac.uk (Piercarlo Antonio Grandi) writes: pcg> People do IPC using pipes or System V MSGs or sockets which cost pcg> far far far more. peter> And the performance costs of this, and other results of getting peter> the MMU so intimately involved with things, is the main reason peter> why a 27 MIPS SparcStation 2 doesn't seem any faster than a 0.7 peter> MIPS Amiga 1000. I still beg to differ. The cost of IPC is not that enormous, as IPC is not that inefficient, and even when it is it is not that frequent. Even under traditional Unix, where a pipe often implies six copies of the same data (source->stdio buffer, stdio buffer->system buffer, system buffer->disk, disk->system buffer, system->buffer stdio buffer, stdio buffer->target), IPC cannot account for one or two orders of magnitude of inefficiency. Even more importantly a very poorly designed MMU could not either. The ultimate difference between a SPARC 2 and an Amiga is not that one has an MMU and the other has not, it is that for one inefficiency does not matter or increases sales, while the other is sold to people that purchase it with their own money. This has amazing effects on how sloppily the system software gets written, and on how easily vendors can get away with it. A non sloppily designed and used MMU has a negligible effect on virtually all applications, and possibly substantial benefits. -- Piercarlo Grandi | ARPA: pcg%uk.ac.aber@nsfnet-relay.ac.uk Dept of CS, UCW Aberystwyth | UUCP: ...!mcsun!ukc!aber-cs!pcg Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@aber.ac.uk