[Beowulf] Opteron downrates DDR400 to DDR333 performance?
V. B. Hunt
shoalcreek5 at gmail.com
Fri Feb 3 13:40:29 EST 2006
Nate Faerber wrote:
> On Thu, 2006-02-02 at 14:05 -0600, NazarioJose at JohnDeere.com wrote:
>> Hello, computer gurus -
>> do any of you know if the AMD Opteron downrates the PC3200 400 MHz DIMMS
>> (DDR400) to 333 MHz (DDR333) performance when the system has more that 2
>> Gbytes of memory installed?
>> i was told that when an opteron socke has more that 2GBytes of memory, then
>> the cpu will automatically downrate the memory rate to an equivalence of
>> DDR333 memory.
> It doesn't necessarily depend on the amount of memory installed. It
> depends on the total number of ranks in your memory DIMMs which is
> likely determined by the number of DIMMs installed. You get downclocked
> to PC2700 once you hit 8 ranks total on a memory controller (one per
> Opteron CPU.) So you could get 4GB of RAM on a processor if you use
> single ranked DIMMs.
> See section 188.8.131.52 here:
> Find previous coverage of this subject here:
That makes much more sense than the little "benchmarking" article I
found. If I had more time, I may have found the white paper from AMD,
but had to cut my search short to go pick up my daughter from half-day
kindergarten (that and I don't often build Opteron machines for my
customers, as most of my customers need mostly individual desktop
machines for light-weight home use).
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