Computer only showing 6gb of 8gb Memory Installed

I just noticed that my computer is only using 6gb (5.75 gb usable) of the 8gb of memory installed

My system

Phenom II X2 555
Msi 785g-e51
Patriot Memory (2) 2gb DDR3 pc 10600 (1) 4gb DDR3 pc 10600
Radeon HD 6950 2gb


I downloaded Memtest the other day and ran it for about an hour and no errors were detected.

While playing wow I occasionally get a blue screen with a physical memory dump

On occasion when returning to computer after its gone to rest state and trying to wake i end up at the "safe mode" screen where it reboots

Not sure if these are at all related but would like to atleast get my comp to recognize all the memory installed.


Thanks for any help or insight you may have....not sure if i need to set something in the bios or???
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  1. What version of windows are you running?

    My guess is windows 7 basic? which is capped at 8gbs

    2gbs for video card
    .25 is my guess for the memory I/O devices

    so that would put you at 5.75gbs left available for your ram.

    Here's a link that might help explain it.
    http://msdn.microsoft.com/en-us/library/aa366778(v=vs.85).aspx
  2. The proper configuration for your motherboard is 2 dimms or 4 dimms, NOT 3 dimms. 1/3 dimms makes you run in single channel mode which hurts your performance.
    2/4 dimms makes you run in dual channel mode. Your motherboard manual explains this.

    However, that would not be the reason your missing 2gb of available ram. I'm guessing that you have 2gb allocated to your onboard video. You should be able to disable this via bios or windows.

    Blue screen issues your having are likely caused by your memory settings being incorrect in bios. Assuming all 3 dimms you have are the same speed, timings, and voltage, you need to go in bios and set these manually, auto does not always set it correctly. You can find the speed, timings and voltage on the sticker on the dimms themselves.
  3. Thank you for your replies

    To clarify the Radeon Hd 6950 is a discrete graphics card with 2gb of memory, does not borrow memory from system.

    The memory upon further investigation...i removed each stick and ran them independantly to see if i just had a bad stick or bad dimm slot and they all checked out to run fine. But what i did see was that as they are labeled as being 2gb sticks in very small print they say "1gb x2" these were given to me from a friend and i didn't see this before as if was almost illegible. So I'm hitting on all cylander's except the missing 256mb of memory which is most likely being used by the onboard graphics, which was disabled when i added the discrete graphics, but may have been turned back on when i cleared cmos and would explain why i have a device driver not installed at boot-up.

    I will recheck the memory settings to make sure the timings are ok....I looked earlier and everything was set to auto so will double check the timings.

    This was my first build so learning as i go, I did not know that you had to use an even number of dimms, don't remember reading that in the mb manual but will double chk as well. with the cheap prices on memory I ordered 2 x 4gb more memory my plan was to have 12gb total but per the 2/4 dimm for dual channel i will need to order another stick...or can i use one of the 1gb chips for a total of 13gb?

    Again thx for your replies and thx for explaining dual channel vs. single channel and dimm slots.

    Sorry for my oversight on the actual memory size "always read the fine print"!!
  4. Nobody stated your discrete graphics card is barrowing system memory, not sure where your getting that from....

    Yes for dual channel configuration and best performance dimms need to be installed in pairs (except X58 chipset requires 3/6 dimms for triple channel config)

    I'm not sure what your thinking, but just use the 2x4gb kit your buying, don't try to mix and match 3 different types and 3 different sizes of ram, your just asking for issues, besides if they are not all the exact specs your going to have problems.

    I see absolutely NO reason why that system would need more than 8gb of memory. 4gb of memory is enough for the average user, and that's a below average computer.

    Your question about adding a 1gb dimm to make 13gb makes it seem like your not paying attention. That would NOT be a dual channel configuration.

    Like I said, your issues are likely related to incorrect dimm bios settings. You seem to think that you only need to check the timings, again, it seems your not paying attention. I said you need to manually set the SPEED, VOLTAGE, and TIMINGS, not just the timings.
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