Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site turtlevax.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!genrad!decvax!decwrl!turtlevax!ken From: ken@turtlevax.UUCP (Ken Turkowski) Newsgroups: net.micro.68k,net.micro Subject: Re: MC68881 Floating-point performance times Message-ID: <612@turtlevax.UUCP> Date: Fri, 14-Dec-84 17:53:50 EST Article-I.D.: turtleva.612 Posted: Fri Dec 14 17:53:50 1984 Date-Received: Mon, 17-Dec-84 02:33:20 EST References: <263@oakhill.UUCP> <896@utastro.UUCP> Reply-To: ken@turtlevax.UUCP (Ken Turkowski) Organization: CADLINC, Inc. @ Menlo Park, CA Lines: 18 Xref: watmath net.micro.68k:494 net.micro:8914 Summary: No difference in single and double precision speeds In article <896@utastro.UUCP> nather@utastro.UUCP (Ed Nather) writes: >Perhaps the most interesting thing about these timings is that there is >essentially NO PENALTY IN USING DOUBLE vs SINGLE PRECISION in the basic >floating point operations. There has been much discussion on the net >about whether the C language is flawed because is specifies that all >floating operations be done in double precision, despite the "obvious >gain in speed" that would result in using single precision operations >where they offer enough precision. > >Looks like it just depends on whose chip you use. Would you like C to do 64 bit arithmetic in all fixed-point computations, if all you needed was 16 or 32? I'd say that the 68881 wastes a lot of time and power computing the extra bits. -- Ken Turkowski @ CADLINC, Menlo Park, CA UUCP: {amd,decwrl,nsc,spar}!turtlevax!ken ARPA: turtlevax!ken@DECWRL.ARPA