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Dual Socket Motherboards & RAM Module Placement

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March 29, 2013 11:53:25 AM

So I just bought a Dell PowerEdge 2950 to tinker with, it came with one CPU and I just bought a different matching pair on EBay along with new RAM. When putting this RAM in, do I have to place it in specific banks for both processors to each get their own? Ive never dealt with something like this before but I've been reading some things that lead me to believe this is the case.

The hardware owners manual doesn't specifically talk about the placement of RAM when using dual CPU's so I'm not really sure.

Thanks in advance!
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March 29, 2013 12:14:58 PM

The manual on page 89 describes the channel concept and witch socket belongs to witch channel. You will get the best performance from adding four stick, one per channel (1,2,3,4 or 5,6,7,8,)
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March 29, 2013 1:03:06 PM

That page does not speak of sockets, aside from the RAM sockets. It talks about two branches, and each branch having two channels. Does each branch belong to a CPU socket?
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a c 115 à CPUs
March 29, 2013 1:37:22 PM


Each CPU socket has its own DIMM bank. Each DIMM bank has quad-channel capability.

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March 29, 2013 1:41:09 PM

So could you be more clear on how those banks are divided between the processors? In the manual it refers to branches which is a term I haven't heard before, is each branch assigned to each CPU socket?

What I plan on doing right now based on what I gather is to place a ram module in slots 1 and 5, 3 and 7. This would place two sticks on branch 0, channel 0, and two sticks in branch 1, channel 2.
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a c 108 V Motherboard
a c 156 à CPUs
March 29, 2013 2:03:56 PM

You put them in 1,2,3,4. That puts 1 stick per channel so you utilize all channels. The manual states "sockets must be populated by lowest number first."
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March 29, 2013 2:09:04 PM

Yeah I saw that, the only thing was that the old RAM modules were not placed like that, which made me think there was more to it than just sticking them in there. It makes sense though as far as dual channel is concerned.
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March 29, 2013 6:00:24 PM

Just put in the new sticks and realized the banks weren't in numerical order. :)  Silly me. So yeah the previous modules were in the 1234 slots, as are the new ones.

Another question would be why, since I bought the server with one CPU, were the sticks in 1234 banks, wouldn't that mean that half of it was going to a non-existent CPU or am I not understanding this correctly?
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a c 108 V Motherboard
a c 156 à CPUs
March 29, 2013 7:59:52 PM

The ram controller is on the mobo so will control it all. Ram should be in every other slot.
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March 30, 2013 3:01:21 AM

As k1114 said, this is an old server with the memory controller in the chip set. Only new cpus have there own memory controllers.
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March 30, 2013 12:59:10 PM

Awesome thank you. Makes sense.
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