Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 9/27/83; site hplabsc.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!houxm!mhuxr!ulysses!allegra!mit-eddie!godot!harvard!seismo!hao!hplabsc!dsmith From: dsmith@hplabsc.UUCP (David Smith) Newsgroups: net.micro.68k,net.micro Subject: Re: MC68881 Floating-point performance times Message-ID: <2312@hplabsc.UUCP> Date: Thu, 27-Dec-84 15:11:55 EST Article-I.D.: hplabsc.2312 Posted: Thu Dec 27 15:11:55 1984 Date-Received: Sat, 29-Dec-84 03:46:35 EST References: <263@oakhill.UUCP> <896@utastro.UUCP>, <612@turtlevax.UUCP> <276@ist.UUCP> Organization: Hewlett Packard Labs, Palo Alto CA Lines: 15 >I remember in my student days using an IBM 370/165 and discovering that >double was FASTER than single precision floating, since the microcode >did everything in double precision and the single ops were done by padding >the operands and truncating the results..... > >Maybe that is the rationale for C working in double.... C grew up on the Pdp-11/45 and /70, which had a mode bit to specify whether floating point was to be done in single or double precision. The C implementation did everything in double to avoid forcing the compiler to change and track the mode bit. David Smith Hewlett-Packard Laboratories