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From: stever@videovax.UUCP
Newsgroups: net.arch
Subject: Re: Floating point performance
Message-ID: <1989@videovax.UUCP>
Date: Sat, 11-Oct-86 15:16:29 EDT
Article-I.D.: videovax.1989
Posted: Sat Oct 11 15:16:29 1986
Date-Received: Sun, 12-Oct-86 13:46:56 EDT
References: <340@euroies.UUCP>
Reply-To: stever@videovax.UUCP (Steven E. Rice, P.E.)
Organization: Tektronix, Comm Group, TV R&D
Lines: 49

In article <340@euroies.UUCP>, Roger Shepherd (shepherd@euroies.UUCP)
writes:

> I was interested to read Ian Kaplan's (...!loral!ian) appeal
> for microprocessors with fast floating point.  . . .

> For example, Ian quotes some performance figures as
>  
>    Intel 80287       < 0.1 MFLOP  (say 0.95 MFLOP at 8Mhz?)
>    National            0.1 MFLOP
>    Motorola            0.3 MFLOP

Shouldn't the figure in parentheses for the 80287 be 0.095 MFLOP??

> To these I'll add the figure for the INMOS transputer (no
> co-processor, floating point done in software)
>  
>    Inmos IMS T414-20   0.09 MFLOP (typical for * and /,
>                                    + and - are slower!)
>  
> According to the figures I have to hand, these processors
> compare somewhat differently when the Whetstone figures are
> compared.  For example, I have single length Whetstone
> figures as follows for these machines
>  
>                                  kWhets   MWhets/MFLOP
>                                                     (normalised)
>    Intel 80286/80287    (8 Mhz)   300         3.2      1.0
>    NS 30032 & 32081    (10 Mhz)   128         1.3      0.4
>    MC 68020 & 68881 (16 & 12.5)   755         2.5      0.8
>  
>    Inmos IMS T414B-20             663         7.4      2.3
>  
> The final column gives some feel for how effective these
> processor/co-processor (just processor for the T414)
> combinations are at turning MFLOPS into usable floating
> point performance.

As one who has looked at the relative merits of various processors
and coprocessors before making a selection, I am not at all concerned
about "how effective [a] processor/co-processor combination[] [is] at
turning MFLOPS into usable floating point performance."  The bottom
line for an application is closely tied to the numbers in the "kWhets"
column.  The real question is, "How fast will it run my application?"

					Steve Rice

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