Would a CPU work if installed only into the 2nd socket instead of 1st?

April 2, 2017 12:56 AM

Sorry for the over simplified question title.... I meant to ask: On a dual processor motherboard, would a CPU work if skipping the first socket and install into the 2ns socket?

I acquired a workstation that has a broken 3rd memory slot (one end where it holds the ram split). I would like to add memory to it but seems it's not going to work. The second CPU socket and memory slots are all unused and in good condition so I wonder if moving the CPU and ram to the second socket and slots would work. I know this is a weird question but would like any possibility before replacing that whole motherboard.

The board is HP SYSTEM BOARD 761510-601 with one Xeon processor and 16GB ram installed.

posted by lanhan to Computers & Internet (4 answers total)

If you have all the hardware, just try it. It might not work, but it's not gonna like fry any components or anything
posted by aubilenon at 1:48 AM on April 2, 2017

Best answer: I would have to disagree on the first commenter's "not gonna like fry any components." It probably shouldn't, but unmounting and moving what is probably an expensive Xeon CPU if you are not doing this kind of work on a regular basis is risky. The typical Xeon E5 CPU is at a minimum hundreds, and potentially thousands, of dollars, and electrostatic discharge (ESD) kills chips and boards. Some of us have electronics shops with extensive ESD remediation in place, but even so, it is uncomfortable to unsocket a several thousand dollar CPU. The pins on socket 2011 are easily damaged and basically unfixable once damaged, and you also have to fully and properly clean and repaste and mount the heatsink, which requires special chemicals and supplies, so this is a lot of work and risk and expense just to try something that shouldn't work.

As for the OP question: Usually this can't and won't work. I can't speak to your particular board, but I'll deem it as "shouldn't work" based on:

http://imagescdn.tweaktown.com/content/7/4/7497_28_tyan-s7076-intel-c612-server-motherboard-review.png

If you look at the design of a typical Wellsburg platform, CPU 0 hosts the Direct Media Interface link to the Platform Controller Hub, which is where all your low speed peripherals are. CPU 1 accesses these resources indirectly through QuickPath Interconnect, which allows CPU 0 to act as a proxy of sorts. These things are fundamentally designed to have socket 0 filled.

While I have not pulled the tech specs on your particular board, and assuming that this was even possible, switching sockets would also impact which PCIe slots are usable. This might be the correct chassis/board:

http://h20195.www2.hp.com/V2/GetPDF.aspx/4AA5-4045ENW.pdf

and you could look at Pages 8-10 for more insight into that issue.

Again, iff this is the manual for your chassis, Page 24 suggests that you can achieve a 32GB configuration by populating DIMM1 and DIMM8 with 16GB modules.

You have at least two potential solutions:

1) Use larger DIMM modules. These boards support modules up to 128GB per module. I don't know if they'll accept generic ECC RDIMM or not, but if they do, 32GB modules like the Samsung M393A4K40BB1-CRC are around $250, and so installing a pair for $500 would get you 64GB in two DIMM modules. You would need to research what is actually compatible with your board. Try sticking two larger modules in DIMM1 and DIMM8.

2) Install a second CPU of a matching type in the second socket, which would also carry with it the benefit of enabling the remainder of your workstation's PCIe slots.

You can also experiment with installing additional modules in non-recommended slots, though this should not be done randomly. If you currently have memory in DIMM1 and DIMM8, try removing the module in DIMM8 and moving it to DIMM2. If this boots and tests without issue, it implies that you have a good chance of being able to populate 1, 2, 7, and 8. However, the system may prohibit this from actually working.
posted by jgreco at 6:42 AM on April 2, 2017 [6 favorites]

Response by poster: Thank you guys! I have tried some scary experiment as you suggested; unfortunately, the board seems not detecting anything in DIMM2 slot so I will scratch the idea of adding my existed memory and go a reasonable price 2nd CPU and use the memory with it. Wonder would that even worth it.

Thanks for the info and suggestion, I am really glad you know what I was asking about, haha! Thanks again!
posted by lanhan at 10:05 PM on April 6, 2017

Well, it'll chew even more power and be able to compute tall sums in a single bound, but as long as there's nothing else wrong, it is likely to work.
posted by jgreco at 12:55 PM on April 10, 2017