I need to order RAM for a Dell PowerEdge server. It came with 4GB RAM.


  • 4 UDIMM slots, support up to 32GB
  • 1600MT/s DDR3
  • Error Correction Code (ECC) memory

I would like to add 8 or 16GB RAM. I see ECC RAM is double the price of normal memory. At first I intended to add 2x8GB, but if it's possible to add only one 8GB module to get 12GB total, that would be great.

Can I add just one module of 8GB, and still keep using the current 4GB?

  • Check the specifications of the PowerEdge server you have in question, if it supports non-ECC memory, it will be indicated by Dell. – Ramhound Apr 12 '17 at 21:08

I believe it is best practice to add RAM in pairs in most situations, but can work. my understanding is that pairing RAM has performance benefits.

Some system architectures require this.

You can however mix ECC and Non ECC Ram, which may reduce the cost, but bear in mind that doing so will disable Error checking. (Source :- Crucial Forum Post)

  • It came with one 4GB module, so it works with one module, and will work with one 8GB module. But I hope it will work with 1x4GB + 1x8GB. I suppose I cannot pair them, but there are four slots, two pairs of two, so each pair of slots gets one module. – SPRBRN Apr 12 '17 at 9:56
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    It does depend on the server motherboard etc. if it's working with one currently, adding another won't break it. If you go for a an 8gb size module, put it in a slot that isn't paired with the 4gb filled slot. If you then get another 8gb, pair that with the existing 8gb. – Stese Apr 12 '17 at 9:58
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    Be careful, adding uneven dimms will make them work in asynchronous dual channel mode. Which means (for your case) that you will have 4GBx2 of dual channel (fast memory), and 4GB of single channel RAM (with half the bandwidth). Depending on what are you doing with that server this may limit performance with high loads. – Neil Apr 12 '17 at 10:27
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    @SPRBRN Yes, Having 2x the same module would be an improvement over two different types of module – Stese Apr 12 '17 at 12:03
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    having 8x1 + 4x1 will work at Async Dual channel, means the system will be seeing 4GBx2 (dual channel) + 4GBx1 single channel. If you want to have the full memory in dual channel, you should go for 8x2 configuration :) – Neil Apr 12 '17 at 12:14

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