Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site metheus.UUCP Path: utzoo!watmath!clyde!floyd!vax135!cornell!uw-beaver!tektronix!ogcvax!metheus!howard From: howard@metheus.UUCP (Howard A. Landman) Newsgroups: net.arch Subject: Re: Use Of Multiple Register Sets / Re: RISC perspective - (nf) Message-ID: <218@metheus.UUCP> Date: Thu, 22-Mar-84 02:17:46 EST Article-I.D.: metheus.218 Posted: Thu Mar 22 02:17:46 1984 Date-Received: Sun, 18-Mar-84 08:12:27 EST References: <2747@fortune.UUCP> Organization: Metheus, Portland Oregon Lines: 14 The question in the referenced article was whether interprocess context switches were more or less common than procedure call context switches. Actually, we ASKED that question before designing RISC I. The measurements taken indicated that for VAX UNIX, interprocess switches were about 100 times less frequent than procedure calls. Thus the payoff for handling them in special hardware is also much less. We decided it wasn't worth the effort. I still think that was the correct decision, especially considering that some interprocess switching (e.g. simple interrupts) can be coerced into using the register window mechanism much like a procedure call. (One interrupt which CAN'T be so coerced is the window overflow interrupt, for obvious reasons.) Howard A. Landman ogcvax!metheus!howard