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The PE2950 Manual states:

For best system performance, all four, or eight FBDs should be identical memory size, speed, and technology

I currently have 4x2GB in slots 1-4, and would like to use 2x8GB n slots 5/6, leaving room for future upgrades.

What exactly am I sacrificing in not maintaining equality in all 8 slots?

EDIT: adding two more chips is not possible (thanks murisonc); would it be advisable to install 4x4GB (0r 8GB) chips, rather than sticking with 2GB across-the-board (as the manual recommends)?

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up vote 3 down vote accepted

Sorry, but it won't work. The PowerEdge 2950 can only operate with 2, 4, or 8 DIMMs. Adding 2 DIMMs won't help you. You'll need to add 4 DIMMs or upgrade the ones you have.

Reference the PE 2950 hardware owners manual page 89 and 90. You should have DIMMs currently in slots 1,5 and 2,6.

Also see pages 137 and 138 for the locations of the DIMM slots and the numbering of those slots.

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I cannot believe that I missed that. – mikewaters Dec 4 '10 at 18:00

I'm pretty sure that the manual just says that to cover them if you mix and match, there are almost infinite combos and they can't be responsible for that. You shouldn't have any problems as long as the speed is the same and if your current ram is registered or ECC that you match that too.

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A bit of speed, not too much, no more than 10-15% in absolute pure memory terms at most but you might speed up your overall, system if it's memory constrained,never the slowest memory is WAY quicker than paging to disk.

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