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From: philm@astroatc.UUCP (Phil Mason)
Newsgroups: net.arch
Subject: Re: Mips / MHz
Message-ID: <392@astroatc.UUCP>
Date: Thu, 15-May-86 10:23:59 EDT
Article-I.D.: astroatc.392
Posted: Thu May 15 10:23:59 1986
Date-Received: Fri, 16-May-86 05:38:03 EDT
References: <1363@unc.unc.UUCP> <467@cit-vax.Caltech.Edu> <384@astroatc.UUCP> <1774@gitpyr.UUCP>
Reply-To: philm@astroatc.UUCP (Phil Mason)
Distribution: net
Organization: Astronautics ATC, Madison, WI
Lines: 54

In article <1774@gitpyr.UUCP> kludge@gitpyr.UUCP (Scott Dorsey) writes:
>In article <384@astroatc.UUCP> philm@astroatc.UUCP (Phil Mason) writes:
>>
>>Power is defined to be the time rate at which work is done.  That leaves us
>>in a little bit of a quandry.  What is a unit of work for computer systems?
>>It must be related to how the CPU affects the information it processes.
>
>   What about I/O bound tasks?  Do you want to measure 'floating-point
>division power' or 'BCD addition power'.  
>   Your analogy with earlier machines is quite apt, except that it must be
>pointed out that, as mechanical devices do not all perform the same tasks,
>neither do computers perform the same tasks.  Comparing a can opener and a
>lawnmower is like comparing a System/36 and an array processor.  The lawnmower
>may have more horsepower than the can opener, but it is useless for opening
>cans.  Likewise, the can opener lacks 'lawnmowing power'.  The System/36
>may do a poor job of Fourier transformation, but I'd hate to see something
>like a COBOL payroll program running on an array processor.
>    Computing power CANNOT be measured in one scalar number.
>-- 

Yes, I agree.  I didn't say it was going to be easy.

Let's look at it this way. There are a number of generic information processing
functions that a computer performs : Floating point, Integer, Program
control flow and I/O operations. There are also subdivisions of these tasks
according to the size and type of the operands (i.e., scalar, vector, array -
8, 16, 32, 64+ bits etc.). A matrix of performance parameters could be 
created in such a way as to give an end user the capability to weigh the
various performance figures for his/her major tasks.  Careful software
simulation and instruction analysis can outline what operations are critical 
for the application. The performance table can then be weighted with the 
results of the simulation and a final number derived from the weighted table
as to the suitability and performance for a particular computer for a 
particular task.

General comparison between computers can be made in this fashion as well.
If a CRAY 2 performs on more types of data and faster in every category 
than another computer, the CRAY 2 is a higher performance machine. Without
application specfic information, there can be some machines that have most
of the performance figures greater than another, but there might be some
parameter of perfomance that is very heavily utilized by an application that
would make the overall majority comparison false.

Comments??


-- 
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Kirk  : Bones ?               Phil Mason, Astronautics Technical Center
Bones : He's dead Jim.        {Your Favorite System}!uwvax!astroatc!philm

My opinions are mine and not necessarily those of my employer.
(I would like to think that my employer believes in them too.)  :-)
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