[Beowulf] X5500 - ECC Registered or Unbuffered?

Kilian CAVALOTTI kilian.cavalotti.work at gmail.com
Thu Apr 2 02:41:48 PDT 2009

On Thursday 02 April 2009 06:44:53 Joshua Baker-LePain wrote:
> AFAIK, the only difference is available capacity (well, and price of
> course).  You can't get unbuffered DIMMs bigger than 2GB.  Also note that
> memory speed goes down as you add more DIMMs per channel (it's also a
> function of CPU clock speed).  So if you want a fair bit of memory (read,
> more than 12GB) but also want to run it as fast as possible, you'll need
> to buy Registered DIMMs (and a fast enough CPU).

Registered DIMMs use registers (hence the name) to buffer signals, for a 
better signal integrity, which allow increased clock rates and slot capacity. 
This is done at a cost of an higher latency, though.

On the Tylersburg platform, if you only plan to use 2GB DIMMs, and no more 
than 1 DIMM per memory channel, unbuffered is probably the way to go. It will 
get you a maximum of 6GB per processor, though. If you want a higher total 
capacity and still keep the maximum frequency (1333MHz), you'll need 
registered DIMMs.


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