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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: is Vax addressing sane today
Date: Sun, 06 Oct 2024 07:18:59 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>Native POWER is, I think, called pSeries. It continues to sell in its own 
>right because it offers high performance--high enough to earn a few 
>ongoing spots near the top of the Top500 supercomputer list.

Looking at the June 2024 edition, I see Summit as the highest-ranked
system with Power CPUs, and they are Power 9.  So if your claim was
true that the Top500 supercomputer list reflects CPU performance,
Power 9 would beat Power 10 in CPU performance, and EPYC, Xeon,
Fujitsu A64FX and Nvidia Grace are more powerful CPUs.  However, in
most supercomputers (including Summit) the GPGPUs provide the bulk of
the FLOPS that are measured in the Top 500, so looking at the Top 500
is misleading for determining CPU performance.

So let's look at SPEC CPU instead.  For CPU2017, I see only four
entries from IBM, all for the Integer Rate metric, two with Power 9
and two with Power 10 CPUs.  The highest of those results is:

base peak
1700 2170 IBM Power E1080

That's with 8 sockets, 120 cores, and 960 threads.  Looking at other
8-socket machines, I find

base peak
3820 3880 BullSequana SH80

That's with 8 sockets, 480 cores, and 960 threads (similar results
from Fujitsu PRIMERGY RX8770 M7, HPE Compute Scale-up Server 3200,
Inspur TS860G7 and Supermicro SuperServer SYS-681E-TR, all done with
Xeon Platinum 8490H CPUs).  And if you go for maximum performance,
there's a 16-socket Xeon machine from Bull with base=7400, peak=7450.

Alternatively, you can instead buy a 2-socket system with similar
performance to the 8-socket IBM Power E1080:

base peak
1950 2140 ASUS RS720A-E12-RS12

and similar results from other systems with the EPYC 9754.

https://www.spec.org/cpu2017/results/res2021q3/cpu2017-20210814-28679.html
https://www.spec.org/cpu2017/results/res2024q3/cpu2017-20240701-43944.html
https://www.spec.org/cpu2017/results/res2023q2/cpu2017-20230522-36617.html

Admittedly, IBM extracts the most performance from each core, but with
only 15 cores per CPU (where others have 128), that is no longer that
impressive.  Nevertheless, neither machines with the Ryzen 7950X nor
with the Xeon-E2488 reach the performance per core (and no results for
the Ryzen 9950X have been submitted yet), so it looks like Power 10
has a really good multi-threading implementation.

The fact that IBM has not submitted results for Power for SPEC CPU
2017 for (Int or FP) Speed or FP Rate results is an admission that
their numbers there are even less impressive.

In any case, certainly for the stuff I do I see no reason why I would
consider, much less recommend buying a Power machine these days.  My
guess is that the major reasons for buying pSeries machines these days
are legacy software and IBM salesmanship.

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>