From owner-freebsd-hackers Fri Jan 15 15:36:59 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA02364 for freebsd-hackers-outgoing; Fri, 15 Jan 1999 15:36:59 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from smtp04.primenet.com (smtp04.primenet.com [206.165.6.134]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA02357 for ; Fri, 15 Jan 1999 15:36:52 -0800 (PST) (envelope-from tlambert@usr04.primenet.com) Received: (from daemon@localhost) by smtp04.primenet.com (8.8.8/8.8.8) id QAA22925; Fri, 15 Jan 1999 16:36:40 -0700 (MST) Received: from usr04.primenet.com(206.165.6.204) via SMTP by smtp04.primenet.com, id smtpd022665; Fri Jan 15 16:36:31 1999 Received: (from tlambert@localhost) by usr04.primenet.com (8.8.5/8.8.5) id QAA20785; Fri, 15 Jan 1999 16:36:10 -0700 (MST) From: Terry Lambert Message-Id: <199901152336.QAA20785@usr04.primenet.com> Subject: Re: TSS and context switch To: thorpej@nas.nasa.gov Date: Fri, 15 Jan 1999 23:36:10 +0000 (GMT) Cc: dillon@apollo.backplane.com, rvb@cs.cmu.edu, rminnich@Sarnoff.COM, bf20761@binghamton.edu, freebsd-hackers@FreeBSD.ORG In-Reply-To: <199901150436.UAA08145@lestat.nas.nasa.gov> from "Jason Thorpe" at Jan 14, 99 08:36:27 pm X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > I distinctly remember there being several instructions on the VAX that > were like this (perhaps the polynomial evaluation instructions.. it's > been a while :-) ... you were better off open-coding them than using > the single instruction :-) Many VAX instructions, especially on lower end processors, like the uVAX II, or instructions which were somewhat deperecated, were emulated in software. For these instructions, if you didn't really need "the full effect", then the emulation tended to be slower. There's also the issue of whether the geometry of the problem was already suited to the instruction, or if there was work going in and out (which was most likely duplicated going in and out of the emulation, as well, transforming it back to be suitable for discrete instructions). One of the people I went to school with, Val Kartchner, did an "infinite" precision math library using VAX assembly. He could tell you very accurately which instructions were emulated on which VAXen. All I can rememebr is the CRC32 instruction on the uVAX... Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message