Windows Server 2008 R2 Standard - Usable RAM is 50% of installed RAM

Posted on 2012-09-10
Last Modified: 2012-09-20
Hi Experts,

We have a box running Windows Server 2008 R2 Standard.
We recently replaced the RAM with 4 sticks, each of 2 GB (the same 4 sticks worked OK in another PC).

Now Windows Computer Properties reports:

Installed memory (RAM): 8.00 GB (3.99 GB usable)

Is there something we need to do to make all the RAM usable?

Question by:LeighWardle
    LVL 14

    Expert Comment

    are you sure that this server is r2 not sp2?

    It looks like you have 32 bits system - it is maximum it will support - to support more then 4GB you will need 64 bits R2 system

    LVL 18

    Accepted Solution

    First question is: is it 32- or 64-bit system? If it is 32-bit, then it is normal and you won't get more than 4 GB out of it.

    Second question is, did you populate DIMM slots with RAM modules properly? There are 2 or 3 memory controller channels and each has many banks. You must populate them with RAM modules in order:
    first RAM into 1st channel, 1st bank,
    second RAM into 2nd channel, 1st bank
    third RAM inot 1st channel, 2nd bank
    fourth RAM into 2nd channel, 2nd bank
    (this is for 2-channels controller)

    Third question is, did you check the BIOS - DIMM slots might also be disabled.
    Also, some servers support RAM Mirroring setup, which gives you only half of RAM usable.
    This is all setup in BIOS.

    Fourth question, are all RAM modules of the same type and speed? There might be difference in SIZE, but must NOT be difference in speed.
    LVL 1

    Author Comment

    Windows Server 2008 R2 Standard only comes in 64-bit.
    LVL 10

    Assisted Solution

    Try moving the sticks of ram, install them in reverse order of what they are now.  Fixed a similar issue I had with a high-end windows 7 machine that had ECC.
    LVL 10

    Expert Comment

    Also, is this a Dell?  I know I've seen some BIOS options on a few Dell servers that will allocate ram as "Spare" instead of normal or "optimized".  Have you checked your BIOS for any weird ram options?
    LVL 1

    Author Closing Comment

    Hi Guys,

    I decided to buy 16 GB (4 x 4GB) to replace the 50% functioning 8 GB.

    We couldn't afford to have any server downtime if we attempted to move the 4 x 2 GB sticks.

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