Path: utzoo!mnetor!uunet!mcvax!ukc!strath-cs!jim
From: jim@cs.strath.ac.uk (Jim Reid)
Newsgroups: comp.sys.hp
Subject: Re: hp9000 ser. 500 hpux
Message-ID: <881@stracs.cs.strath.ac.uk>
Date: 16 Mar 88 11:41:52 GMT
References: <987@maccs.UUCP> <4760006@hpfcls.HP.COM> <672@kuling.UUCP>
Reply-To: jim@cs.strath.ac.uk
Organization: Comp. Sci. Dept., Strathclyde Univ., Scotland.
Lines: 21

In article <672@kuling.UUCP> irf@kuling.UUCP (Bo Thide) writes:
>............. So the logical question here is:  Why doesn't HP have a
>multi-CPU 800?  Was the experience with the 500 series so bad that HP has
>given up that idea?

No, it's probably because building closely-coupled multiprocessors that
use RISC (eg the 800 series CPU) isn't easy. RISC architectures like to
have on-chip caches, N-deep pipelines and all sorts of things like that.

This causes horrendous problems when you try to keep the value of shared
variables (eg kernel data structures) consistent. eg CPU #X updates
some variable, while CPU #Y still has an old copy in its cache and
CPU #Z is just about to fetch an even older copy from its register file.

		Jim
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