When can I use all 8gigs of my memory MS???

Discussion in 'Windows 64bit' started by Defjr, Mar 30, 2008.

  1. Defjr

    DevilsPGD Guest

    In message <> "Tony Sperling"
    In a x64 capable system, instead of 4GB you have a 64GB physical address
    space to work with (on today's CPUs and chipsets), the bar is raised

    With an address space capable of 16 exabytes, we won't hit a hard limit
    any time soon, and frankly, if you did build a system with 16 exabytes
    of RAM today, you probably wouldn't mind the few KB lost to real mode
    BIOS, nor the ~640MB-1GB lost to hardware.
    DevilsPGD, Apr 13, 2008
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  2. Undoubtably, so. Only, I wasn't talking about address space at all - I was
    talking about the amount of installed physical memory!

    Tony. . .
    Tony Sperling, Apr 13, 2008
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  3. Colin Barnhorst, Apr 13, 2008
  4. Actually, if we are to believe Microsoft articles, to avoid driver
    compatibility issues they *do* throttle the available RAM to 3.12GB on
    Vista 32-bit SP1. I'm not 100% sure but I think that disabling DEP (nx
    AlwaysOff) may remove the limit and allow users to see a bit more RAM if
    the hardware is using less addresses than the imposed limit.

    I'm not sure how Windows 32-bit XP2 handles the driver compatibility
    issues. If you have an XP SP2 box with 4GB RAM Colin, you could do
    tests with and without the /nopae switch (DEP disabled or enabled) and
    let us know the results. Disabling PAE automatically disables DEP.

    John John (MVP), Apr 13, 2008
  5. The 3.12GB is just an example given in a KB explaining why all 4GB are not
    available to the user. The actual number varies according to the system.
    3.12GB has become a kind of urban legend due to folks not paying attention
    to the fact that the author states he giving an example.
    Colin Barnhorst, Apr 13, 2008
  6. Microsoft *specifically* states that on Vista SP1 the available RAM is
    *limited* to 3.12GB.

    John John (MVP), Apr 13, 2008
  7. Defjr

    Zootal Guest

    I just booted to XP SP2 32 bit using the /nopae switch, and it still told me
    I had 3.00 GB of ram. This is an Asus M2A32.MVP board, Phenom 9600, 4GB of
    ram (four 1GB sticks). I'm open to playing with this if anyone has any ideas
    as to what I could do to get it to see more memory in XP32. I don't use
    XP32, and I have the partition backed up, so I'm not concerned about
    corrupting it to the point of needing to be wiped and restored.

    XP64 tells me I have 4.00 GB ram.
    Zootal, Apr 13, 2008
  8. Defjr

    dennis Guest


    *For example*, the System Information dialog box *may* report 3,120
    megabytes (MB) of system memory on a computer that has 4 GB of memory
    installed (4,096 MB).
    dennis, Apr 13, 2008
  9. You're pretty well stuck with what Windows XP 32-bit is telling you.
    There is no way around the problem other than moving to the 64-bit
    platform, or start yanking devices out of the box!

    John John (MVP), Apr 13, 2008
  10. Yes, it also *may* report 2.75GB. Read further on down below, Microsoft
    specifically states that Vista 32-bit *limits* RAM to 3.12GB. If that
    is not the case there is an error in the KB article.

    John John (MVP), Apr 13, 2008
  11. Defjr

    dennis Guest

    Yes, it *may* report anything. In the beginning they use 3.12 as an
    example (they use the word example), and I strongly believe that this is
    also the case in the end, they just don't want to write "for example" again.
    dennis, Apr 13, 2008
  12. I strongly believe that the KB article is right and that for driver
    compatibility reasons the RAM is limited to 3.12 GB.

    John John (MVP), Apr 13, 2008
  13. Defjr

    dennis Guest

    Driver compatibility is about not going above 4 GB, which is possible
    when Windows go into pae mode. So available RAM is 4 GB - memory mapped IO
    dennis, Apr 13, 2008
  14. Even with PAE enabled 32-bit Windows workstation versions cannot access
    RAM above the 4GB arena. I shall agree to disagree with your
    interpretation of the KB article and hope that a Microsoft engineer
    informs us of the facts.

    John John (MVP), Apr 13, 2008
  15. From the KB:

    "For example, the System Information dialog box may report 3,120 megabytes
    (MB) of system memory on a computer that has 4 GB of memory installed (4,096

    Colin Barnhorst, Apr 13, 2008
  16. Dennis is correct.

    Colin Barnhorst, Apr 13, 2008
  17. Check the manual for your mobo on your options for closing memory holes and
    such. You probably can gain a small amount but not the whole thing.
    Colin Barnhorst, Apr 13, 2008
  18. Defjr

    Zootal Guest

    I moved to 64 bit XP last year. I keep a 32 bit XP install on another
    partition for those times when I need it, but that is very seldom now that I
    have 32 bit Win2000 running in a VM. It's more of a curiosity for me then
    anything else.
    Zootal, Apr 13, 2008
  19. Defjr

    Zootal Guest

    It's not worth the trouble. XP 64 is my main OS on this box, XP32 is there
    just in case.
    Zootal, Apr 13, 2008
  20. So you are saying that the KB article is wrong?

    John John (MVP), Apr 14, 2008
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