Re: PPC vs. Intel Spec Marks revisited

From: Achim Gratz (gratz@ite.inf.tu-dresden.de)
Date: Thu Apr 17 1997 - 07:08:59 CDT


Hugh LaMaster <lamaster@nas.nasa.gov> writes:

> While we are on this subject, it is curious that the (200 MHz?) Ultra II
> is slower in all categories than the 170. Is the bus interface
> slower? I think the 170 runs at clock/2, and I thought the 200 was
> supposed to also, but since the performance seems lower than the 170,

That's right. Interconnect bandwith for 200MHz Ultra machines scales
with the CPU frequency. Ultra2 machines have four banks of memory,
while Ultra1 has two.

> I'm wondering what is going on.

I have explained this already, but since you obviously missed it, here
it goes again:

The values for Ultra1-170 are obtained with the F77 version of stream
(not by me), while the values for the Ultra2-2200 were done with the C
version. That prevents certain optimizations the compiler would
otherwise be happy to do. I have not submitted numbers for F77 for a
simple reason: they are not as interesting to me as the C numbers.
The numbers in the table are first shot aggregate numbers that suffer
a bit from the load that had been on the machine at the time of
measurement. I had submitted more recent results (both standard and
experimental) with a parallelized version of stream to John McCalpin,
but they never showed up in the table, I assume they've been lost.
I'm going to resubmit them, here's the (unofficial) summary of the
standard results.

------------------------------------------------------------------
Machine ID ncpus COPY SCALE ADD TRIAD
------------------------------------------------------------------
Sun_Ultra2-2200 2 291.4 285.6 329.9 311.4
Sun_Ultra2-2200 1 228.5 227.5 258.9 189.9
Sun_Ultra1-200E 1 218.2 213.0 235.7 188.0
Sun_Ultra2-2170 2 266.4 264.5 311.8 276.8
Sun_Ultra2-2170 1 198.8 192.1 207.6 168.0
Sun_Ultra1-170E 1 196.2 192.4 222.9 157.9
Sun_Ultra1-140 1 178.7 175.7 202.9 154.4
Sun_SS20-712 2 78.6 79.6 84.0 85.0
Sun_SS20-712 1 62.6 60.2 58.6 60.2
Sun_SS20-612 2 79.0 77.6 82.1 82.5
Sun_SS20-612 1 55.9 57.3 54.5 59.7
Sun_SS20-51 1 47.7 43.1 44.4 44.7
Sun_SS20-502 2 82.9 78.7 92.7 91.0
Sun_SS20-502 1 68.1 53.4 76.4 67.7

Achim Gratz.

--+<[ It's the small pleasures that make life so miserable. ]>+--
WWW: http://www.inf.tu-dresden.de/~ag7/{english/}
E-Mail: gratz@ite.inf.tu-dresden.de
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