Date: Fri, 15 Jan 1999 23:36:10 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: thorpej@nas.nasa.gov Cc: dillon@apollo.backplane.com, rvb@cs.cmu.edu, rminnich@Sarnoff.COM, bf20761@binghamton.edu, freebsd-hackers@FreeBSD.ORG Subject: Re: TSS and context switch Message-ID: <199901152336.QAA20785@usr04.primenet.com> In-Reply-To: <199901150436.UAA08145@lestat.nas.nasa.gov> from "Jason Thorpe" at Jan 14, 99 08:36:27 pm
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> 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
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