[Beowulf] X5500 - ECC Registered or Unbuffered?
sp at numascale.com
Wed Apr 1 19:22:22 EDT 2009
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?
Registered DIMMs = higher density (i.e larger in storage size), but
typically with a latency penalty since there is a register on the dimm
for Address/Control signals that delay them by 1 clock cycle. So your
CL4 Ubuffered DIMM would become a CL5 Registered. In addition Registered
DIMMs have a PLL on the module to "freshen" up the clock signal.
Unbuffered DIMMs cant have so high density (i.e many chips) on them
because of load to the control/address signals (more load = lower signal
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