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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
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