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Supermicro PDSGE 955X and CM2X1024 6400PRO


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I just put together a Supermicro PDSGE 955X board with a Pentium D 840 and a pair of XMS2 CM2X1024 6400PRO sticks.


It turns out I'm having trouble with using Dual DDR2 with this combination.

I have these in the blue slots for interleaved memory as Supermicro suggests and I'm getting some pretty abysmal scores using default SPD ( 5-5-5-15 @ 667 )


Using Everest v2.20.405 and SiSoft Sandra 2005 SR3 1069 for testing I get the following:


In "dual channel mode" I get:


Read = 2105MB/s (slower than a 1.7 P4 with PC2100)

Write = 386MB/s (slower than a 1.6 P4 with PC133)

Latency = 252ns (Yuck!)



RAM Bandwidth Int Buf'd iSSE2 = 5048

RAM Bandwidth Float Buf'd iSSE2 = 2073


Turns out I get roughly the same scores when both sticks are installed in any combination of slots.


In single channel (1 stick installed)


Read = 5107MB/s

Write = 1981MB/s

Latency = 89.6ns



RAM Bandwidth Int Buf'd iSSE2 = 4515 MB/s

RAM Bandwidth Float Buf'd iSSE2 = 4500 MB/s


I tested both sticks one at a time and there were no differences.


Big difference in scores here.


Any ideas?

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It may not be important, but I noticed something in running the tests with both sticks installed (in any combination of slots).


The LEDs start out "full" (all segments lit) and after a couple of seconds slowly drop off to the first red pair.


With a single stick installed, all LED segments are fully lit during the test.


Seems odd as I wouldn't think the chipset would back off on the speed during heavy usage, but who knows. Also wondering if this could also be related to voltage. The BIOS doesn't allow changing voltage so can't check that.


Supermicro is (of course) saying the memory isn't certified for this board, but can't say why it wouldn't be compatible. I'm trying to follow up on that one.


Their current memory list for this board is at:




I'm trying to find the difference between the XXXXXXXXX one mentioned on their list and the Corsair.


Here's the XXXXXXXXX datasheet.



I REALLY want to get the Corsair to work, but having doubts at this point.


Give me a break - you can't put competing company names in posts?

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I verified from Supermicro that the DDR2 voltage is fixed at 1.8 and was able to verifty that's what I'm getting using their monitoring utility.


If you overclock, the bios will raise the voltage to 1.9 and I was able to verify this. I raised the FSB to 210Mhz and was getting 700Mhz on the memory side.

This didn't make a difference when both modules are installed.


Since there's no hope of getting these to work with this board, I'm returning them. Very dissapointed that these couldn't work at all when both of them are installed and Corsair doesn't have any "normal" support.

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