memory voltage, and quad ranked vs dual

Crucial's site is a fairly trustworthy source for determining what kind of memory will work: http://www.crucial.com/store/listparts.aspx?model=PowerEdge%202950%20III

For an explanation of memory "rank", see http://www.kingston.com/literature/pdf_files/mkf_753-2_memoryranks.pdf
 

Hi Callandor,

Thanks for your response - I'd already checked both of these resources, and they didn't seem to answer my question(s)...

If you use lower rank RAM (ie, dual or single rank), you will get less capacity, but performance should not be affected.  It will probably end up costing more overall because you'll need more RAM modules to achieve the same total RAM.

To find out what you currently have in the server, CPU-Z is a good tool to use: http://www.cpuid.com/cpuz.php

Thanks Callandor - I'm a bit nervous about running the CPU-Z software, although it does look like it would give me the info I need. The server in question is in a live environment, and there's a FAQ on the website:

Q3: CPU-Z causes a general protection fault, or freezes my system, or causes a blue screen.

I guess I'll just have to bite the bullet and pick up what looks the nearest spec memory and hope for the best!

Crucial (and Kingston, I think) guarantees that their selector choices will work in your machine, so hopefully that means there is a high probability of success.

I started to suggest CPU-Z ... but ran it to confirm it would show the ranks -- and it does not.    Not sure if it will do so with registered/FBDIMM modules or not.     However, it should still provide the info you need, as the SPD tab will let you confirm the exact make/model of your installed RAM modules ... from which we can identify their exact characteristics (voltage, rank structure, etc.).

You can mix modules of different ranks ... but each pair has to be the same => and you can't use modules that require different voltages.     Other than that, I'd trust the Crucial and/or Kingston selectors to identify the correct modules.

Dell's documentation for this sytem doesn't reference the total rank capacity of the memory controller ... but they sell the system with up to 8 dual-rank DIMMS installed, so as a minimum it clearly supports at least 16 ranks.     I would definitely buy dual-rank modules if possible -- this will leave you additional room for expansion if 16 ranks turns out to be the limit.

Hi Garycase - thanks for your input - we already have Quad ranked in there (2 x 4GB Quad Rank) - I'm assuming you would recommend more quad rank rather than dual? I'm nervous about the CPU-Z utility for the reasons I stated above - do you know any other way to get the model/make for the installed ram?

Here is the compatible memory modules for the PE 2950 and PE 2950 III(click the compatibility link on the right to confirm)
http://accessories.us.dell.com/sna/products/Memory_Upgrades/productdetail.aspx?c=us&l=en&s=bsd&cs=04&sku=A2257233&mfgpid=193378

I notice Dell doesn't mention quad rank in there specs but Kingston does.
Here are Kingstons compatible modeles
http://www.ec.kingston.com/ecom/configurator_new/partsinfo.asp?root=us&LinkBack=http://www.kingston.com&ktcpartno=KTD-WS667LPQ/8G

Perhaps a check on Dells site using the Service tag will give you the  part number for the ram under "Original System Configuration" tab found here. You may be able to get the specs from that.
http://support.dell.com/support/topics/global.aspx/support/my_systems_info/details?c=us&cs=555&l=en&s=biz&~tab=1&~ck=mn

Thanks - Everest did the trick. We'd already tried contacting Dell Support, and the website with the service tag - both turned up nothing useful. Everest gave us the answers we needed, and the RAM is being fitted today.