Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!att!cbnewsh!wolf
From: wolf@cbnewsh.ATT.COM (thomas.wolf)
Newsgroups: comp.sys.atari.st
Subject: Re: UNIX -- ATW Speed
Message-ID: <5188@cbnewsh.ATT.COM>
Date: 30 Oct 89 17:16:38 GMT
References: <545@nikhefh.nikhef.nl>
Reply-To: wolf@cbnewsh.ATT.COM (thomas.wolf,ho,)
Organization: AT&T Bell Laboratories
Lines: 38

>>>      4 megabytes of RAM, upgradable to 120 meg
>>>      With all 4 boards, that is 13 transputers, the machine
>>>       runs at 10 MIP (= 1/5 Cray)
>>I guess this should be at least 100 Mips, because ONE T800 can run at 10
>>Mips.
>
>Somehow I doubt the Cray uses an 8 MHz 68000 for file IO ....
>

These claims are very misleading in that they imply that a system with 13
transputers will actually run a program 1/5th as fast as a Cray (I'm assuming
the above MIPS figures are correct.)  _Each_ T800 has a processing power
of 10 MIPS (the upper limit at which instructions can be processed.)  So
if you have a calculation-intensive application, say one that does ray-tracing,
you can expect that peek to be reached.  If you ran this same program on
a 13-transputer based ATW, I doubt whether you will see significant increases
in performance, since that application will be run on a single T800 (unless
it was specifically written with parallelism in mind - using OCCAM(I guess that
is the T800 assembly language?) - I don't think there are compilers smart
enough to take conventional C programs and parallelize them.)

I am not familiar as to how applications have to be written to run on a CRAY,
but my guess is that you can use conventional C programming.  So if you took
the above program, recompiled and ran it on a CRAY, you _would_ see significant
speed improvements  (if 100MIPS = 1/5 Cray, I guess the program would run
at 500 MIPS?)

In any event, benchmarks of the above type are useless unless they are placed
in the right context.  Yes, some programs run just as quickly on an Apple II
as on a CRAY, given enough restrictions on what the program does.

Tom

-- 
+---------------+-----------------------------+  I don't remember,
| Tom Wolf      | Phone:  (201) 949-2079      |  I don't recall,
| Bell Labs, NJ | E-mail: twolf@homxb.att.com |  I have no memory,
+---------------+-----------------------------+  Of anything at all. P. Gabriel