Re: Maximum attainable memory bandwidth

From: Patrick F. McGehearty (
Date: Fri Oct 18 1991 - 16:14:25 CDT

Sorry for my lack of response. We are getting ready to ship an
compiler release, new products, etc, etc :-) But enough excuses.

The real reason for the delay is that I decided to run it by marketing for
their pro forma approval before sending results for a publishable
benchmark, as a courtesy. Then I found out that the appropriate people were
out of town (customer visits, SuperComputing '91, etc) and won't be back for
a little while. Having started this route, I feel I have to wait for a
acknowledgement, so I have no offical results to report. I will let you
know when I hear something, but I don't expect anything for another week
at least.

Unofficially, compiling fc -O2 generates real*4 vector code,
while fc -O2 -pd8 generates real*8 vector code. [The -pd8 says
set default real/integer length to 8]. On the C2 and C3200
product line, there is almost a factor of two difference between
the measured results for these two options, since the clock rate
is the same for both, but real*4 works on 4 bytes at a time while
real*8 works on 8 bytes at a time. Preliminary results show no
major surprises, but there are still plenty of holes in the
chart of C3200/C3400/C3800/ 1-4 processors.

- patrick

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