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Thread: Showing Usable RAM 2.75GB while installed is 4GB

  1. #1
    electrosam is offline Junior Member
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    Default Showing Usable RAM 2.75GB while installed is 4GB

    Hello.
    I have installed 2 modules of Gskill 2GB DDR31600MHz hence total memory is 4GB. But in the Properties of computer it is showing usable memory as 2.75GB. 512MB is assigned to on board ATI Graphics. So it should show 3.5GB usable memory.

    Motherboard is Gigabyte GA-MA785GM-UD2H & Processor is AMD Phenom II X4 955.

    Why this is happening ? Please help me out.

  2. #2
    mv2devnull is offline Member
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    32-bit OS (Windows) can address only 4 GB of RAM, but some of those addresses have to be reserved for communication with devices. This is a well known problem and it does depend on the installed devices, BIOS, and Windows, how much address space is reserved.

    A 32-bit OS with PAE (Physical Address Extension) could do extra magic to be able to address more and thus have all of the 4 GB available. But 32-bit desktop Windows is no such OS.

  3. #3
    Psycho101's Avatar
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    All 32bit Windows versions use PAE, at least according to the properties page on every single XP install I've ever done. The reason it is still restricted to 4Gb or less is to maintain driver compatibility (many software programs and drivers specifically designed for 32bit Windows would fall over in normal use if asked to go to/address anything outside 4GB). A full list of OS's using PAE is here: Physical Address Extension - Wikipedia, the free encyclopedia

    Any way, the fact that only 2.75GB is usable does seem on the small side. The least amount of RAM I would have expected to see on a 32bit install like that is 3.25GB. Where an additional 500MB has gone to is a mystery.

    Is there any reason why you haven't installed the 64bit version of Windows 7? You get both versions included. There's no disadvantage to using 64bit Windows, it is backward compatible with 99.9% of 32bit apps and has excellent driver support. With such a modern system and 4GB of RAM, installing a 32bit OS is a waste.
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  4. #4
    mv2devnull is offline Member
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    While all Windows now might have "PAE", they don't in practice use it for what one expects for PAE. Effectively same as not having it. If I load 32-bit PAE Linux kernel on machine with 8 GB, I have 8 GB to use. That is how I understand PAE.

    OEM copies of Windows are sold as either 32-bit or 64-bit, while the Full package includes "choose 32 or 64" license, AFAIK. And yes, I too would choose a 64-bit these days.

    Could the integrated graphics eat that 0.5 GB of addresses?

  5. #5
    Psycho101's Avatar
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    I would have (from the system specs etc) thought that including the integrated GPU's share of RAM there should still be over 3GB left.

    Going over all possible components that have onboard RAM and which have it addressed by the system (HDD cache isn't included for example as only the HDD uses it internally, CPU cache is included) I can't myself figure out why there would be so little remaining. There would be L1, l2 CPU cache, any reserved space used for system comms and maybe BIOS shadowing etc, any cache on the network cards and sound. Also anyother add in cards may or may not have RAM that will be prioritised an address space.

    I have an image of XP that I use occasionally. With this RIG, even though I have 1GB of graphics RAM to address I still have 3GB to play with. I'm going to image to XP in a minute, so I'll have a look exactly how much RAM I have available for use.

    I forgot about the OEM/For System Builders version being just a single DVD of either 32bit or 64bit. Fortunately the OEM product keys will all register either version. If the OP can get hold of the 64bit instalation files then he could use the 64bit version. This is of course a morally grey area , but IMO if you've bought the copy and have a legal key, swapping it for the 64bit version isn't a crime.
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  6. #6
    mv2devnull is offline Member
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    In Device Manager there is "View Resources by Type" option (at least in Vista). The addresses are in hex, but in principle that list should show the culprit. (example of odd bits that one can stumble on with Google)

    electrosam?

  7. #7
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    sounds okay to me

    ~3.2GB of 4GB are available for x86 (32bit) minus 512MB for onboard sums up to ~2.7Gb something available.

    looks plausible to me
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  8. #8
    Psycho101's Avatar
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    In a 32bit environment, initially 4GB or there abouts should be available. I'm not sure where you got 3.2GB from. 3.2Gbwould be the amount approx that would be available on a system with 4GB AFTER 512MB had been deducted for the GPU, not before.
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  9. #9
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    her we go - screenshot task manager when 4GB installed:



    available are 3.3GB system ram

    If the motherboard does not have physically (additional) "vram" onboard then that ram is taken away from those 3.3GB.

    So the OP got left what it shows..
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  10. #10
    Psycho101's Avatar
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    Default Re: Showing Usable RAM 2.75GB while installed is 4GB

    You don't seem to understand.... What ever free RAM is shown in Task Manager on your system will be AFTER your VRAM Has been addressed. The same should be true of the OP, however much more RAM is missing than the mere 512MB used from system RAM. That taken RAM is not going to be addressed twice, just once.

    4GB minus the OP's 512MB from the common pool for the VRAM = 3.5GB, minus a couple of hundred for caches etc etc (the available RAM is never simply just Installed RAM minus GPU RAM) should leave around 3-3.25Gb for Windows.

    If 2.75GB is the correct amount he should be seeing then please explain why I have ~3Gb available on this system when it runs XP? I have 1GB of Video RAM to be addressed, the OP has only 512MB.
    Coolermaster CM 690 II advance Case
    Corsair HX750 (CWT, 91%(80+ Gold rated @230V) single 62A 12V rail
    P55A-UD4 v2.0 @ F14
    Core i5 760 @ 20 x 201, 4.02GHz
    TRUE Black with a single Noctua NF-P12 pumping out 55 CFM @ 19db .
    2 x 2GB Mushkin Ridgeback (996902), @ 7-10-8-27, 2010-DDR, 1.66v
    2 x Gigabyte GTX 460 1024MB in SLI (Pre OC'd to 715MHz core and 1800MHz VRAM) @ 850 Core / 4100 Mem.
    Intel X25-M Boot Drive (OS and Programs) 200MB/s Read & 90MB/s Write
    Corsair X32 200MB/s Read & 100MB/s Write
    WD Caviar Blue 640GB C (Steam, Games, Storage, Temp Files & Folders, etc)
    Samsung F3 500GB Backup/Images
    Noctua 1300RPM 19dB case fan (rear extraction)
    3 x 140 MM Coolermaster LED fans (one front intake, one top extraction, one side intake)
    Dell Ultra Sharp 2209WAf E-IPS @ 1680x1050

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