Newsgroups: comp.parallel
From: ifunltd@xs1.xs4all.nl (ifunltd)
Subject: Re: Performance of T805 & T425?
Organization: XS4ALL, networking for the masses
Date: 12 Apr 1995 08:28:51 GMT
Message-ID: <3mje2l$ss4@usenet.srv.cis.pitt.edu>

Steffen Jahn (stjahn@eva.cs.TU-Magdeburg.DE) wrote:
: Performance of Inmos T805 & T425?

: I need some performance infos of these both transputers for my 
: practical work. Can anybody tell me the processing velocity in MIPS & 
: MFLOPS.

About the T805 running at 30 MHz:
The late Inmos said it would do 4.3 MFlop/s peak, I got it to 5.0 MFlop/s,
but in real applications you should expect to get between 1 and 2. The
*application* I ran only used the FPU and no RAM access, plus there were
only additions in it, i.e. pretty useless except to set the world record
transputer-Flop/s, like I did.

About the MIPS for both T805 and T425, they are easy to calculate, but
there the same variability in achieved MIPS can be expected: the parts 
run at 30 MHz, and they do most basic instructions in one cycle, i.e. 
they should do 30 MIPS under ideal circumstances (the entire program
and data should fit in the 4K internal RAM, and no complex instructions
should be used, i.e. only 13 real instructions left, with operands between
0 and 15). As soon as you access external memory (either for code or for
data), divide the obtainable MIPS by a factor 3-4, depending on the speed
of your DRAM. When you do real applications, expect to reach 30% of the
peak performance: then you will have done quite a good job in my opinion.

But: use an OS or certain types of compilers, and you would do better on
a low-budget PC.

Good luck and have fun !

JANG at IF UnLtd

