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Thread: 4GB RAM limit in memory test on Satellite A100

  1. 4GB RAM limit in memory test on Satellite A100
    #1
    Beginner
    Join Date
    May 2008
    Posts
    3
    Hi,
    I just installd 4gb ram. The (updated) BIOS shoes 4gigs in bios setting, but the memory test will only go to 3071 MB
    I checked the two rams single - the check goes to the full 2gb in both cases... So where has the 1GB ram gone?
    Toshiba sais, that my notebook supports up to 4gig ram, I have a Toshiba A100 - 153 (PSAA9e), Bios version 6 Phoenix CSS 2005 Q4 Version Mak -r1.53
    Ram support up to 800 MHz FSB

    Has anyone gon an idea?

  2. Re: 4GB RAM limit in memory test on Satellite A100
    #2
    Enthusiast
    Join Date
    Mar 2007
    Posts
    104
    Hi friend,

    man thats easy to solve. You must only read this [article from TAbBlogger.com|http://blogs.msdn.com/hiltonl/archive/2007/04/13/the-3gb-not-4gb-ram-problem.aspx] and this [Toshiba Support Document|http://aps2.toshiba-tro.de/kb0/TSB82022E0000R01.htm].

    Everything will be clarified and you will be enlighted about the fact that the system itself without the operating system needs also his amount of RAM to work properly.

    Thats it, nice weekend

  3. Re: 4GB RAM limit in memory test on Satellite A100
    #3
    Beginner
    Join Date
    May 2008
    Posts
    3
    Thanks for the quick answer,
    Before I posted in this forum I read google suggestions for my problem. But I didn't give up - so I posted. So to clarify my question: The Phoenix BIOS does show 4GB mem in the bios menu - but the system memory check (on boot, before any OS could do anything) only shows 3071MB. So I thought: how could the OS detect more than 3071MB, if the system only detects as much.
    I could try another OS (eg RetHad Fedora) but that wouldn't make any difference, would it? As the lapi should support 4GB - I think at least the memory check should show 4GB...?
    So what's wrong?

  4. Re: 4GB RAM limit in memory test on Satellite A100
    #4
    Senior Member
    Join Date
    Apr 2008
    Posts
    462
    I'm not 100% sure but I think this is how it works:

    The BIOS detects the physical size of the memory (two 2GB sticks), whereas the system memory check tests the available memory it has access to. The rest of the memory is mapped/locked to the VGA card and other PCI devices. Writing to the mapped memory while the VGA card is using it would cause major corruption.

  5. Re: 4GB RAM limit in memory test on Satellite A100
    #5
    Beginner
    Join Date
    May 2008
    Posts
    3
    So if I got it right:
    My board can adress 4 GB memory, 512 for the VGA (not shared) - remain 3,5 GB - 500 mb lost for any devices... and there are my 3gb...
    But with a 32 bit system I can adress *2^32^* Bytes a GB is 2^30^ Bytes, so I have *2^2^ = 4 GB* to adress all memory.
    However I bought a gb too much and for all further threads and everything:
    the 4GB memory - problem is no OS problem. With a 32 bit system the cpu (or to be more exact the MMU) can only adress 4GB memory and this includes VGA memory...
    Thanks for the advice...

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