Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 beta 3/9/83; site uthub.UUCP Path: utzoo!utcsri!utai!uthub!thomson From: thomson@uthub.UUCP (Brian Thomson) Newsgroups: net.micro.68k,net.micro.16k Subject: Re: Re: PDP11s vs the micros Message-ID: <223@uthub.UUCP> Date: Wed, 21-Aug-85 10:33:50 EDT Article-I.D.: uthub.223 Posted: Wed Aug 21 10:33:50 1985 Date-Received: Wed, 21-Aug-85 23:30:52 EDT References: <1617@hao.UUCP> <847@mako.UUCP> <2422@sun.uucp> Organization: CSRG, University of Toronto Lines: 17 Xref: utai net.micro.68k:771 net.micro.16k:259 Dave Trissel (davet@oakhill.UUCP) brags about the Motorola FPU: >Concerning floating-point state saves we gave a lot of thought to minimizing >latency times. What we did was give an indication to the OS of whether any >of the FP registers had been used. If not, the OS could skip the context >save and restore completely. Careful reading of the specs for the National FPU, plus a little experimenting, shows that they also provided this capability, though their implementation has the look of being a fortuitous accident (hint: check the behaviour of the Trap Type field of the Floating Status Register). Unfortunately, whoever wrote the documentation made no mention of this use, which suggests that they don't realize what they have and are in danger of making it not work in future releases of the hardware. -- Brian Thomson, CSRI Univ. of Toronto {linus,ihnp4,uw-beaver,floyd,utzoo}!utcsrgv!uthub!thomson