HP's 2-way Opteron server

Rob Stow wrote in message ...
Adam Warner wrote:
Even being the Opty fanboy that I am, when someone publishes
benchmarks showing that a single Opty 248 beating a 3.2 GHz
Xeon dualie the first word that comes to mind is "bullsh*t".

There is this thing called memory latency. Opteron has a lot
less of it with the on-chip memory controller than Zeon does
with the frontside bus.

Mitch

Mitch Alsup wrote:

Rob Stow wrote in message ...

Adam Warner wrote:
Even being the Opty fanboy that I am, when someone publishes
benchmarks showing that a single Opty 248 beating a 3.2 GHz
Xeon dualie the first word that comes to mind is "bullsh*t".


There is this thing called memory latency. Opteron has a lot
less of it with the on-chip memory controller than Zeon does
with the frontside bus.


I'm well aware of that. However, that conveys an advantage
that typically lets an Opty dualie beat out a Xeon dualie that
has a 50% higher cpu clock. This particular benchmark had
a single 2.2 GHz Opty beating - by a huge margin - a 3.2 GHz
Xeon dualie. I suspect the result was reported incorrectly -
it probably should have been a dualie vs dualie result.

Rob Stow writes:

[HP DL145 vs. DL140 webbench 5.0 results]

This particular benchmark had a single 2.2 GHz Opty beating - by a huge
margin - a 3.2 GHz Xeon dualie. I suspect the result was reported
incorrectly - it probably should have been a dualie vs dualie result.

For both systems, single and dual processor results were reported
and contrasted, so your "should probably have been" is probably
a bit unfounded.

Anybody here who is familiar with webbench 5.0, who could comment
on the relative importance of better memory controller, better
system interconnect, larger L1 caches, and/or double the L2 cache?

best regards
Patrick

Russell Wallace wrote:

Steve Thompson wrote:

It can depend strongly on the code. One of my main
compute-intensive tasks, a molecular dynamics code
that is certainly not a meaningless test, is as fast
on a 1.4 GHz Opteron as on a 3.2 GHz P4.

I'm curious - any idea what features of the Opteron are
responsible for the performance advantage on this code?

Opteron:
L1 Icache = 64 KB
L1 Dcache = 64 KB
L2 cache = 1024 KB

Northwood:
L1 trace cache = 12000 µops
L1 Dcache = 8 KB
L2 cache = 512 KB

Perhaps his code and/or data are too large to fit inside Northwood's
L1 caches, yet small enough to fit inside the Opteron's L1 caches?

Also, Northwood is not very good at shifts and integer multiply,
compared to the Opteron.

Rob Stow wrote:

Mitch Alsup wrote:
There is this thing called memory latency. Opteron has a lot
less of it with the on-chip memory controller than Zeon does
with the frontside bus.

I'm well aware of that. However, that conveys an advantage
that typically lets an Opty dualie beat out a Xeon dualie that
has a 50% higher cpu clock. This particular benchmark had
a single 2.2 GHz Opty beating - by a huge margin - a 3.2 GHz
Xeon dualie. I suspect the result was reported incorrectly -
it probably should have been a dualie vs dualie result.

Why not? A dual Xeon has a single shared bus to the chipset. If you run two
memory-latency dependent programs on both Xeons, they'll go through the
same bottleneck; typically, you expect the same total throughput as with a
single Xeon running just one program. Now, on the Opty (nice nick ;-), you
have half the latency, and no shared bus, so a single Opty should get
double performance, and a double Opty should get four times (almost;
there's the round trip from the cache coherency).

We've got an Athlon 64 recently, and tried some benchmarks. With my own CPU
intensive microbenchmarks, the Athlon 64 is clock-by-clock as fast as the
old Athlon; nothing gained. However, with our applications (EDA CAD, e.g.
synthesis), there's a factor two difference. The most stunning experience
however is KDE 3.1. It's really fast on the Athlon 64, you barely notice
program startup time (it feels definitely faster than KDE 3.2 on an Athlon
XP, though the KDE people did tune a lot there). KDE program starting
definitely is a memory intensive job, latency bound (linking lots of shared
C++ libraries together). Also, starting up Cadence design framework
(exactly the same workload) was a lot faster than anywhere else.

I think the latency problem is a real one. You won't see it on SPEC, since
really very few SPEC programs are memory latency bound (and if they are,
people will hack the compiler to remove that). Real bloatware (and we have
to use real bloatware everyday, unfortunately) however is.

--
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://www.jwdt.com/~paysan/

On Fri, 27 Feb 2004 10:55:36 -0600, Rob Stow
wrote:
Mitch Alsup wrote:
There is this thing called memory latency. Opteron has a lot
less of it with the on-chip memory controller than Zeon does
with the frontside bus.

I'm well aware of that. However, that conveys an advantage
that typically lets an Opty dualie beat out a Xeon dualie that
has a 50% higher cpu clock. This particular benchmark had
a single 2.2 GHz Opty beating - by a huge margin - a 3.2 GHz

That "huge margin" is only about 15%. Extremely impressive, but not
all that huge. This shouldn't be that big of a surprise though, the
Opteron has been pretty much destroying the Xeon in every web server
benchmark out there. Ace's did a fairly extensive set of tests he

http://www.aceshardware.com/read.jsp?id=60000275

Here are a couple others from the past few months:

http://www.pcmag.com/article2/0,4149,1061586,00.asp
http://www.infoworld.com/article/03/...64linux_1.html

If you look at the SPECweb and SPECwebSSL results it becomes obvious
that the Opteron is not only pretty much owning the Xeon, but in fact
it tends to beat out all comers on a chip for chip basis. The only
processor that is competitive with the Opteron is the IBM Power4+, and
even here the 2.2GHz Opteron 848 chips in 4P configurations are faster
than the 1.7GHz Power4+ 4P setups. Note that software plays a big
role here, so an accurate comparison is a bit tough.

Xeon dualie. I suspect the result was reported incorrectly -
it probably should have been a dualie vs dualie result.

Err, than what in the hell was the second, higher set of Opteron
results for? The results are reported VERY clearly and the make
perfectly good sense.

The Opteron is simply THE chip to have for web serving, this HP test
is just the latest indication of that.

-------------
Tony Hill
hilla underscore 20 at yahoo dot ca