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Hi all, I hope this is an appropriate place to post this question. If not and someone can point me to a forum that may be a better choice for ...
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  1. #1
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    Question Server memory is mystifying!!!


    Hi all,
    I hope this is an appropriate place to post this question. If not and someone can point me to a forum that may be a better choice for hardware questions I would appreciate it...

    As part of my new job I need to better understand server memory compatibility issues, ie various types of servers and what memory modules they can use. I am having one heck of a time finding any reliable info on this because memory sellers only want to promote their own modules that they currently sell, so these are the only modules they list as compatible. I am dealing mostly with older servers that use DDR or SDRAM.

    For example, I am trying to find out if modules I have from a Dell Poweredge 6650 server can also be used in a Dell Poweredge 2650 server. You're thinking, why not just try them and find out, however I do not have access to the servers for testing.

    I have found conflicting information on this question. Many sellers say the memory is not interchangeable but some say they are. The specific modules I have are Micron MT36VDDT12872G-265C2.

    I am also very curious about how to interpret the part numbers from various memory makers.

    Does anyone know a reliable source for information on older memory modules and compatibility with particular servers? Any help would be much appreciated!!

  2. #2
    oz
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    Quote Originally Posted by vsilly View Post
    For example, I am trying to find out if modules I have from a Dell Poweredge 6650 server can also be used in a Dell Poweredge 2650 server. You're thinking, why not just try them and find out, however I do not have access to the servers for testing.
    Welcome to the forums!

    Just curious... have you checked the user manuals for these servers to see what memory each one requires? If you don't have access to the hard copy of the manuals, perhaps you can find them online. Either way, the manual is where I'd look first.

    Of course, some memory vendors have various scanning tools and online charts available to users, but I'm not so sure any of those would really answer your question.
    oz

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    Thanks for your reply!!

    Yes I have looked at pdf manuals online for these servers. It generally just lists a spec for the memory it takes which sounds quite general. But then when I look up specific modules, they tend to say they are compatible with a specific group of servers, despite the specs being apparently compatible with a very wide range of servers.

    So I don't know if this is all being made intentionally obtuse to keep the end users confused or if there is truly a difference. For example there may be one module with Specification "X" that say it works with server A,B,C and a different part number with Specification "X" that is listed as compatible with servers D,E,F. From the specs
    being the same you would think they would work with either.

    So I am uncertain if I lack knowledge about the esoteric technical differences or if it's just marketing on the part of memory makers.

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  5. #4
    Linux Guru bigtomrodney's Avatar
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    That really depends on the motherboard in use. These specs do change and I've seen very different setups with similar model numbers. I'll second ozar and say try to find the manual. Particularly when ECC RAM is so expensive and so fussy, you don't want to make mistakes there

    [e]EDIT[/e] - Apologies...I posted too late there. If you are sure that they are the same speed/spec (e.g. PC-2700) and are both ECC RAM then I would go ahead and plug them in. Often manufacturers list their supported hardware which is often just another form of marketing. If they're playing by the book with regards to the RAM specs it should work fine.
    Last edited by bigtomrodney; 12-17-2008 at 07:06 PM.

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    I deal with this all the time and it can be a real pain. Just today, I got in 30 sticks of memory for Dell 1800's. Because I didn't want to pay 3X the price by ordering from Dell, I matched up the specs and ordered: DIMM 240-pin - DDR2 - 400 MHz / PC2-3200 - CL3 - registered - ECC (Kingston).

    I opened up a machine, added 2 sticks, and booted. The machine comes up beeping/error codes and says "make sure DIMM_1A DIMM_1B, DIMM_2A DIMM_2B all have the same memory type/configuration." When I had put the memory in, I had noticed that one stick is double-sided, while the other is single-sided - but they have identical Kingston part numbers. So I grabbed another stick that is double-sided and put that in with the existing double-sided. The system booted and appears happy. So, *if* I had ordered just 2 sticks of this RAM, it would not have worked because the board was picky enough to sense the actual physical difference in RAM - even though Kingston considers it the same part number.

    While this doesn't answer your question, it illustrates that this isn't an exact science and *will* depend on how picky the system/BIOS is. Most of the time, I can use outside vendors for memory, but it can be more of an art to having a "feeling" that this or that RAM will work.

    In my opinion, the extra work/headache *is* worth it to cut your RAM cost by 60-80%. My method is to match up the memory specs, and then buy it and test. But expect to have some failures here and there.

    The system spec sheet will list the memory type/configurations that are supported.

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