[Beowulf] X5500 - ECC Registered or Unbuffered?

[Joshua Baker-LePain]

On Wed, 1 Apr 2009 at 4:47pm, Orion Poplawski wrote

> Jan Heichler wrote:
>> 
>> Don't forget DDR3-ECC memory which must be registered.
>
> http://www.siliconmechanics.com/i22789/2U-4-node-server.php shows options for 
> "ECC Unbuffered" or "ECC Registered".  No idea what the practical difference 
> would be.  Anyone?

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).

-- 
Joshua Baker-LePain
QB3 Shared Cluster Sysadmin
UCSF