Memory performance on PE R610 (Adv ECC vs Optimizer)

[Stephen Dowdy]

Stephen Dowdy wrote, On 05/29/2009 12:49 PM:

> For comparison...
> I only get about 8GB/s using OpenMP threaded version of STREAM, but
> with 1 proc module, and 1066MHz DIMMs. Should i be seeing better
> than this, and if so, why am i not? (from what you show above, i
> expect to see roughly:
>    0.5 (one socket) * 35000 (yields ~ 17GB/sec) \
>      * 0.8 (1066/1333 scale memspeed) => ~13GB/sec
> Should tri-channel (your setup) versus dual-channel (mine)
> have that much impact?

Dual-Channel (8GB) shows:
> -------------------------------------------------------------
> Function      Rate (MB/s)   Avg time     Min time     Max time
> Copy:        7964.6757       0.0645       0.0643       0.0647
> Scale:       7783.5016       0.0660       0.0658       0.0662
> Add:         8723.6035       0.0884       0.0880       0.0890
> Triad:       8835.4905       0.0875       0.0869       0.0881
> -------------------------------------------------------------

reconfiguring the DIMMs by pulling 1 to go to tri-channel
and 6GB does indeed scale out as expected!
-------------------------------------------------------------
Function      Rate (MB/s)   Avg time     Min time     Max time
Copy:       11869.7313       0.0435       0.0431       0.0440
Scale:      12100.3400       0.0426       0.0423       0.0430
Add:        13497.3580       0.0571       0.0569       0.0575
Triad:      13603.7800       0.0567       0.0565       0.0575

The reason i was want to believe this was that Tom's Hardware
or anandtech did a *windows* based test of the Nehalem and
showed very little bandwidth improvement from dual to tri
channel. (and a significant latency increase)

Perhaps that was an earlier revision of Nehalem-EP's IMC, or
Windows has some issue?

thanks,
--stephen

-- 
Stephen Dowdy  -  Systems Administrator  -  NCAR/RAL
303.497.2869   -  sdowdy at ucar.edu        -  http://www.ral.ucar.edu/~sdowdy/