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    Fedora 13 not recognizing all 4GB of RAM in T60

    Discussion in 'Linux Compatibility and Software' started by UCHacker11, Oct 2, 2010.

  1. UCHacker11

    UCHacker11 Notebook Consultant

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    I just installed Fedora 13 x64 on my Thinkpad T60 and it is only recognizing 2.9 GB of the 4 GB of RAM I have installed. The bios sees all 4 GB and memtest came up with 0 errors in the RAM.

    uname -r :
    2.6.34.7-56.fc13.x86_64

    Any help would be greatly appreciated.
     
    UCHacker11, Oct 2, 2010
    #1
  2. H.A.L. 9000

    H.A.L. 9000 Occam's Chainsaw

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    T60 = 945 Express Chipset
    4GB is recognizable, but not usable.
    3.2GB is usable - MaxDVMT for GMA graphics = 2.9GB.

    Do you have Intel Graphics or ATI? Even a 64-bit OS cannot overcome a 32-bit hardware limitation.
     
    H.A.L. 9000, Oct 3, 2010
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  3. UCHacker11

    UCHacker11 Notebook Consultant

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    thanks a lot. I was going crazy trying to figure that out. I didn't even think of the hardware limitations. I have ATI graphics.
     
    UCHacker11, Oct 3, 2010
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  4. H.A.L. 9000

    H.A.L. 9000 Occam's Chainsaw

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    I guess, then, that instead of the Intel GMA setting aside DVMT memory, that some is being reserved as PCI addressing space, since you have ATI graphics.
     
    H.A.L. 9000, Oct 3, 2010
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  5. stevea

    stevea Notebook Enthusiast

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    No - mem isn't set aside for PCI. PCI is mapped into the mem space. Something is odd/wrong.

    Try this command:
    # head -1 /proc/meminfo
    MemTotal: 7995476 kB

    That's on an 8GB i5 system using the native intel graphics
    # uname -r
    2.6.34.7-56.fc13.x86_64
     
    stevea, Oct 4, 2010
    #5
  6. Pitabred

    Pitabred Linux geek con rat flail!

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    The 945 chipset doesn't properly address memory, so it's actually limited to 4GB of mem space, even in 64bit mode. It has to map the PCI memory into the top of the 4GB mem space because it can't address anything higher, basically "overwriting" any physical memory that would be addressed in those ranges. Which is why he's losing nearly a gig of RAM.

    It really is a hardware limitation, nothing software can do about it.
     
    Pitabred, Oct 7, 2010
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  7. debguy

    debguy rip dmr

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    The top 512MB of 4GB are reserved for high BIOS, DMI, interrupts, apic and PCI-e. Additionally up to 256MB are reserved for shared VRAM, depending on the BIOS. That's the bigger parts of where the max. 3.2 GB RAM come from.
    On the lower end there are approximately another 65MB reserved for low BIOS.

    Here's the data sheet:
    http://www.intel.com/Assets/PDF/datasheet/309219.pdf

    I don't know exactly where the 2.9GB come from. This 300MB difference seems a bit odd. I suspect transient VRAM allocations to be responsible that usually are used to get widescreen resolutions instead of 4:3.
     
    debguy, Oct 7, 2010
    #7