Douglas Bollinger <dcb.TakeThisOut@pa.nospam.net> wrote:
> On Sun, 19 Oct 2003 19:06:09 +0100, Rui Pedro Mendes Salgueiro wrote:
> <snip>
>> This [MSI K8T Master2-FAR] is one of those crippled boards in
>> which only one processor
>> has direct access to the memory (only 4 DIMM slots). This makes
>> its price a bit less attractive than it seems at first look. Tyan
>> has a similar model (Tiger K8W (S2875)), but for some reason I
>> can't find a price for it in pricewatch (not yet released ?).
> <snip>
> Do you have any data to back-up "crippled",
Not really, but it seems quite obvious that forcing the second
processor to access memory through the first (so, extra latency)
is crippling it, but I have not searched for benchmarks. I would
be interested in seeing SPECrate results, but I kind of doubt that
vendors (AMD or others) have benchmarked the "crippled" boards.
I am now looking at the results at:
http://www.spec.org/cpu2000/results/rint2000.html
http://www.spec.org/cpu2000/results/rfp2000.html
AMD has a number of results published. Selecting all the 5 that test
Einux A4800, all 5 have 8x512MB PC2700 DDR ECC Registered SDRAM CL2.5,
so I think they are using both banks (each bank has only 4 slots, right?).
Has C'T published something ? I searched a bit:
<a style='text-decoration: underline;' href="http://www.google.pt/search?q=site%3Aheise.de+opteron+SPECint_rate_base2000" target="_blank">http://www.google.pt/search?q=site%3Aheise.de+opteron+SPECint_rate_base2000</a>
<a style='text-decoration: underline;' href="http://www.heise.de/ct/Redaktion/as/spec/ct032098/" target="_blank">http://www.heise.de/ct/Redaktion/as/spec/ct032098/</a>
<a style='text-decoration: underline;' href="http://www.heise.de/ct/Redaktion/as/spec/ct0309106/" target="_blank">http://www.heise.de/ct/Redaktion/as/spec/ct0309106/</a>
Looking at 2 results, that seem comparable:
<a style='text-decoration: underline;' href="http://www.heise.de/ct/Redaktion/as/spec/ct0309106/newisys/CFP2000.014.html" target="_blank">http://www.heise.de/ct/Redaktion/as/spec/ct0309106/newisys/CFP2000.014.html</a>
<a style='text-decoration: underline;' href="http://www.heise.de/ct/Redaktion/as/spec/ct032098/msi_9130/2cpu/CFP2000.004.html" target="_blank">http://www.heise.de/ct/Redaktion/as/spec/ct032098/msi_9130/2cpu/CFP2000.004.html</a>
The values obtained are quite near (18.6 for the MSI K8T-Master2
(the board which was being discussed) , with 2x1024MB PC2700 Reg-ECC
DDR SDRAM 2533 versus 18.4 for the Newisys with 6 GByte DDR333,
presumably in 2 banks), despite the MSI using AMD Opteron 246
(2000 MHz), while the Newisys uses AMD Opteron 244 (0F50) (1768 MHz) *.
So it seems that the extra memory bank makes a difference.
* the page says "CPU(s) enabled: 1" but this must be a typo,
because the runtimes for two copies of the benchmarks are quite
similar to runtimes for the MSI board, which is said to be using
2 cpus.
A benchmark where the 2 banks should have a big effect would be to run
2 copies of STREAM at the same time (assuming that the OS manages to
put each instance in one CPU and use the local memory, it should be
possible to get near 100% of the bandwidth in both). I found a report
of such a test (in ppt format):
<a style='text-decoration: underline;' href="http://wwwseminars.web.cern.ch/wwwseminars/2003/2003-OtherFormats/t-20030903.ppt" target="_blank">http://wwwseminars.web.cern.ch/wwwseminars/2003/2003-OtherFormats/t-20030903.ppt</a>
In slide 13 there is:
1x Stream: 2x Stream: 4x Stream:
2x Opteron, 1.8 GHz,
HyperTransport: 1006 1671 MB/s 975 1178 MB/s 924 1133 MB/s
2x Xeon, 2.4 GHz,
400 MHz FSB: 1202 1404 MB/s 561 785 MB/s 365 753 MB/s
It is not very obvious what is being reported here, because the
Opteron numbers seem too good. It is understable that the Xeon
numbers are halved going from 1 STREAM to 2 and then halved again
with 4 (shared bus). It is also understable that the Opteron numbers
don't fall much from 1 STREAM to 2. It is less understable that 4
STREAMs are almost as fast than 2, since there are only 2 memory
buses.
I have just run STREAM on my computer and I saw this message:
"Each test is run 100 times, but only
the *best* time for each is used."
So, unless the benchmark is modified**, if one has two copies running
at the same time, it might happen that one manages to do a run while
the other is inactive for some reason (it has already finished, for
instance), and that is the number which will be reported.
** I have not verified if this is already checked. Ignoring the
few first and last runs should be enough to prevent the problem.
> Also, don't forget the form-factor issue, the direct-access boards
> all seem to be huge.
For my purposes, it doesn't matter much. I'll probably use a tower
case, anyway. But such boards are able to fit in a 1U computer.
See the Newisys 2100 on the ppt mentioned above.
--
<a style='text-decoration: underline;' href="http://www.mat.uc.pt/~rps/" target="_blank">http://www.mat.uc.pt/~rps/</a>
..pt is Portugal| `Whom the gods love die young'-Menander (342-292 BC)
Europe | Villeneuve 50-82, Toivonen 56-86, Senna 60-94<!-- ~MESSAGE_AFTER~ -->
>> Stay informed about: opinions on motherboards for AMD Opteron