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We have a HP PROLIANT DL160 G6 as a development server. Recently we decided to upgrade the memory and but this one. So we finish with 2 modules of 2GB that came with the server and the new module of 4 GB.

We tried to install the three of them, but the server fail to start. What could be happening? With only the new one installed it works as normal.

I've been reading a lot about it, but I fail to see the problem. Apparently all the modules have the same speed, the three of them are Registered and the HP guide doesn't say anything about installing an even number of modules.

Somebody has any clue?

The server doesn't boot, so I doesn't have any text error to share. It start doing a lot of noise as normal, but doesn't show anything in the screen and get stuck there.

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Are they all the same rank? – MDMarra Dec 20 '11 at 17:01
up vote 1 down vote accepted

Sure about Registered and Unbuffered RAM? The 2GB are probably Unbuffered. The 4GB is usually registered.

If not, see that you populate according to guidelines. Largest modules closest to CPU, followed by smaller. Each memory bank will denote the first module to be populated.

See: What is the difference between RDIMM vs UDIMM

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Thanks, the problem was that. The web page were I search for the RAM say they were Registered when actually they were Unbuffered. – Julio J. Jan 11 '12 at 8:37

HP has excellent comprehensive docs for all systems. The technical documentation ("QuickSpecs") for the DL160G6 provides guidelines for memory configuration:

  • Do not mix Unbuffered memory (UDIMMs) with Registered memory (RDIMMs)
  • Do not install DIMMs if the corresponding processor is not installed
  • If only one processor is installed in a 2CPU system, only half of the DIMM slots are available
  • To maximize performance, balance the total memory capacity between all installed processors
  • It is not required, but it is recommended to load the channels similarly if possible
  • You can only have up to eight (8) ranks installed per channel
  • You can only install two quad-rank DIMMs per channel
  • You can only install two UDIMMs per channel; if available, the third slot in the channel must remain empty
  • Populate DIMMs from heaviest load (quad-rank) to lightest load (single-rank) within a channel
  • Heaviest load (DIMM with most ranks) within a channel goes furthest from the chipset
  • For memory mirroring mode, channel 3 must be unpopulated. Channels 1 and 2 are populated identically
  • For lock-step mode, channel 3 must be unpopulated. DIMMs in channels 1 and 2 will be installed in pairs. The paired slots will be 1,4; 2,5; 3;6 on a 3DPC system or 1,4; 2,5; on a 2DPC system
  • No mixing DIMM voltage; all DIMMs must be the same voltage

I suppose you have plugged all three modules within the same channel - just plug the third module into the white slot of the next channel and you should be good.

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Thank you for your answer. But the modules were well connected each of them in a separate channel (white slots). – Julio J. Jan 11 '12 at 8:39

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