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I have two HS21 blades for an ibm bladecenter, and I'm having memory problems since I installed 4 DIMMs of 4GB. I suspect the problem is that I bought DDR2 800 instead of DDR2 667, has anyone had problems with this? Is there any way to fix this short of buying new memory?

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Check the CAS (Column Address Strobe) timing of the modules. Often faster DIMMs have longer CAS timings. If this is the case then the memory is probably not compatible with your server. Ebay is your friend.

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The memory worked fine when I had a single quad core package in the blade, it started throwing errors when I added a second quad core package. The memory works fine in another blade with a single dual core package. I just checked, the CAS timing is the same between the 800 and 667 DIMMs. Could the 800 DIMMs produce more heat or something? It seems like it might be a heat problem. – shapr Jun 15 '09 at 17:03
They shouldn't produce more heat than normal DDR2-667 ones if they're running at 667. However, 4GB DIMMs might produce more heat than smaller units if they have large chip counts (i.e. two rows of RAM chips). I do have some machines (HP XW9300s) where extra ducting is recommended if you use larger memory modules. – ConcernedOfTunbridgeWells Jun 15 '09 at 17:13

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