[Beowulf] Woodcrest Memory bandwidth

Vincent Diepeveen diep at xs4all.nl
Mon Aug 14 17:07:12 EDT 2006


Yes very dissappointing bandwidth.
Probably the simple logics is that in a dual machine, 2 memory controllers 
is always
faster than 1.

http://www.cs.virginia.edu/stream/stream_mail/2005/0020.html

2x 2.8Ghz opteron
------------------------------------------------------------- 
Function Rate (MB/s) Avg time Min time Max time
Copy: 9368.0362 0.0039 0.0043 0.0043
Scale: 9206.1106 0.0040 0.0043 0.0047
Add: 9457.6361 0.0057 0.0063 0.0064
Triad: 9499.4051 0.0057 0.0063 0.0064

----- Original Message ----- 
From: "Mark Hahn" <hahn at physics.mcmaster.ca>
To: "Jason Holmes" <jholmes at psu.edu>
Cc: <beowulf at beowulf.org>
Sent: Monday, August 14, 2006 8:04 PM
Subject: Re: [Beowulf] Woodcrest Memory bandwidth


>> Here's a 4 core Woodcrest system with 4 sticks of 2 GB 667 MHz FB-dimms:
>>
>> Function     Rate (MB/s)  Avg time   Min time  Max time
>> Copy:       4813.2590      0.2663      0.2659      0.2675
>> Scale:      4826.2181      0.2656      0.2652      0.2662
>> Add:        5244.0135      0.3664      0.3661      0.3669
>> Triad:      5244.3106      0.3665      0.3661      0.3671
>>
>> This was a pathscale compiled stream executable with openmp using 4 
>> threads.
>
> kinda sucks, doesn't it?  here's what I get for a not-new dual-275 with 
> 8x1G PC3200 (I think):
>
> Function      Rate (MB/s)   RMS time     Min time     Max time
> Copy:        5714.6837       0.0840       0.0840       0.0841
> Scale:       5821.0766       0.0825       0.0825       0.0826
> Add:         6437.8226       0.1119       0.1118       0.1120
> Triad:       6414.2079       0.1123       0.1123       0.1124
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