Article View: comp.sys.intel
Article #1207Re: Any new instructions in a i486?
From: Ian Heavens
Date: Wed, 16 Dec 1992 09:16
Date: Wed, 16 Dec 1992 09:16
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In article <WAYNE.92Dec11164422@backbone.uucp> wayne@backbone.uucp (Wayne Schlitt) writes: > >There have been a fair amount of discussion in comp.sys.intel about >what new instructions the i486 has (and if the Cyrix 486SLC/486DLC >implement them.) > > > >The XADD and CMPXCHG instructions are useful for implementing >semaphores in multi-processor systems. Not something a normal >application would have much use for. > With XADD and the bus lock prefix, you can implement an atomic fetch-and-add on a 486. This is much more useful than test-and-set, the only hardware support for mutual exclusion in the 80386. Building SMP systems from 80386s is a real pain. ian --- Ian Heavens ian@spider.co.uk Spider Software Spider Park, Stanwell Street Edinburgh, EH6 5NG, Scotland +44 31 555 5166 (Ext 4347) --
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Path: arc1-ca.pugleaf.net!sparky!uunet!pipex!bnr.co.uk!uknet!edcastle!spider!raft.spider.co.uk!ian From: ian@spider.co.uk (Ian Heavens) Newsgroups: comp.sys.intel Subject: Re: Any new instructions in a i486? Message-ID: <1992Dec16.091655.7353@spider.co.uk> Date: 16 Dec 92 09:16:55 GMT References: <1992Dec11.201306.18470@udel.edu> <WAYNE.92Dec11164422@backbone.uucp> Sender: news@spider.co.uk (USENET News System) Organization: Spider Systems Limited, Edinburgh, UK Lines: 27 Nntp-Posting-Host: redknee.spider.co.uk