I'm upgrading a Dell R710 from single CPU to dual CPU with Xeon E5630 processors harvested from multiple R710 systems and combining into one. I have 18 2GB UDIMMs to play with, all from Dell configured R710 systems, but cannot get anything to POST beyond 3 sticks for each CPU.

I have read the technical guide and the following two more comprehensive guides:

Installing and Upgrading DDR3 Memory - Quick Reference Guide

Dell™ PowerEdge™ Servers 2009 - Memory - A Dell Technical White Paper

I have concluded from this and other research the following:

(1) The Xeon E5630 supports maximum memory speed of 1066MHz

(2) UDIMM maximum is 24GB which I assume I can split between the CPUs for 12GB each

(3) 2 DPC (DIMMs Per Channel), 3 Channels per CPU, 6 UDIMMs per CPU, 12 UDIMMs total

But I cannot get this to work despite all the RAM working if I use 1 DPC for all 3 channels per CPU.

It should work according to the charts on page 7 of 9 in the white paper with DIMM 0 and DIMM 1 each SINGLE rank as indicated and populated according to the other chart on the same page with 3 Channels Used, 2 DPC using A1, A2, A3 and A4, A5, A6 for CPU 1 and B1, B2, B3 and B4, B5, B6 for CPU 2.

The information gets a little scant about dual processors and think this may be where I'm hitting a limitation. How can I get 24GB of UDIMM running with dual CPUs?


You can't have that many UDIMMs in a server. There are reasons why people use Registered memory... and this is one of them.

You can use a maximum of 12 of those in this server. Each CPU has three channels of three slots each. With UDIMMs, you can only populate two of those channels.

I think you need to keep experimenting and going one step at a time. Try with one CPU first, just in case you have a CPU socket or system board issue.

  • As I explained, I know I can only use 12 UDIMMs and I know I can only use 2 DIMMs per Channel (DPC). I can get it to work with 3 UDIMMs per CPU in A1-A3 and B1-B3 which is 1 DIMM per Channel. Why would I revert to one CPU when I know both are working? – BartmanEH Sep 14 '15 at 1:09
  • Because this is troubleshooting. Try loading one CPU up with the DIMM channels you expect to use. I'm just giving you a suggestion to see if the POST process or errors change. The better suggestion is to use higher-end RDIMMs if you need that capacity. UDIMMs are a bad compromise. – ewwhite Sep 14 '15 at 5:08
  • 1
    After various swaps and researching each part number, one set turned out to be registered and, therefore, not compatible with the rest. Eliminating that set left me with 12 X 2GB sticks. 3 turned out to be dual rank and the other 9 were single rank. It booted up but complained about an unsupported configuration and it would halt after POST requiring an F1 press to continue. That wasn't going to be acceptable and coupled with the fact that there may be issues down the road with this unsupported configuration, I purchased 12 X 4GB of ECC Registered RAM and this seems to be running tickety boo. – BartmanEH Oct 1 '15 at 11:37

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