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64-bit and only "3.87 GB usable"? RRS feed

  • Question

  • Wondering why 64-bit only makes small improvements; it recognizes 3.87 GB while 32-bit sees 3.25 GB.
    Norton AntiVirus 2009
    Saturday, March 28, 2009 1:38 PM

Answers

  • Does your motherboard automatically assign memory for a built in video card?  This will cause Windows to report the memory that's available after the BIOS subtracts the onboard video memory.

    More info on how memory works in the WDDM here:  http://blogs.msdn.com/tmulcahy/archive/2009/02/11/windows-and-video-memory.aspx
    - John
    • Proposed as answer by llynne Sunday, March 29, 2009 5:05 PM
    • Unproposed as answer by Adam M MCP Thursday, May 28, 2009 2:41 PM
    • Marked as answer by Ronnie VernonMVP Monday, June 1, 2009 7:07 PM
    Sunday, March 29, 2009 4:20 AM
    Answerer
  • RAM modules are designed to disable sections recognised as faulty during POST. You may have a partial failure of one of the modules. Memtest and similar diagnostic utilities will not reveal this since the faulty memory sections are disabled, not active but faulty.

    Remove each of the dual-channel pairs separately (consult your motherboard manual to find which DIMM slots are the matching pairs, usually the pairs are adjacent slots but they can be alternate slots) to find which pair includes the defective module. The defective pair will report 1.91GB or so to the BIOS at POST instead of 2.04GB.

    Memory modules often have lifetime warranties, so you may be able to obtain a replacement from the memory manufacturer.
    Monday, March 30, 2009 6:30 AM
  • Tech0utsider,

    I'm currently running Windows 7 x64 RC, and with a supported motherboard, Windows only identifies 3.25 GB of my 4 GB as usable, whereas this memory is detected and used fine under Windows XP and Windows Vista. There are still some kinks in Windows 7's memory model, and I imagine that they'll be ironed out for the final release.
    -Alex
    Thursday, May 28, 2009 4:38 PM

All replies

  • How Much RAM do you physically have fitted, and are you sure youve installed the x64 version? I'm Running Windows 7 64 bit with 6GB of Ram and its reporting 6.00GB of RAM.

    What does it say when you right click on Computer and select Propeties?
    Saturday, March 28, 2009 2:42 PM
  • I have 4 sticks, each 1 GB. Yes, I have the x64 version. I know because my w7 reades 3.87 GB while wXP x32 only reads 3.25 GB.
    Norton AntiVirus 2009
    Saturday, March 28, 2009 3:10 PM
  • Does your motherboard automatically assign memory for a built in video card?  This will cause Windows to report the memory that's available after the BIOS subtracts the onboard video memory.

    More info on how memory works in the WDDM here:  http://blogs.msdn.com/tmulcahy/archive/2009/02/11/windows-and-video-memory.aspx
    - John
    • Proposed as answer by llynne Sunday, March 29, 2009 5:05 PM
    • Unproposed as answer by Adam M MCP Thursday, May 28, 2009 2:41 PM
    • Marked as answer by Ronnie VernonMVP Monday, June 1, 2009 7:07 PM
    Sunday, March 29, 2009 4:20 AM
    Answerer
  • Is a chipset/Bios Problem, old Motherboards suports 4GB, but they need some memory (about 300MB) to handle it.

    Regards,

    AdlerBR
    • Proposed as answer by llynne Sunday, March 29, 2009 5:04 PM
    • Unproposed as answer by Adam M MCP Thursday, May 28, 2009 2:41 PM
    Sunday, March 29, 2009 3:41 PM
  • Does your motherboard automatically assign memory for a built in video card?  This will cause Windows to report the memory that's available after the BIOS subtracts the onboard video memory.

    More info on how memory works in the WDDM here:  http://blogs.msdn.com/tmulcahy/archive/2009/02/11/windows-and-video-memory.aspx
    - John
    No. According to the Windows Performance Index Printout, 0 MB of system memory is dedicated to the graphics card.

    My Computer supports up to 8 GB of memory. It is fairly recent (mid 2008)

    Norton AntiVirus 2009
    • Edited by TechOutsider Tuesday, March 31, 2009 1:10 PM wrong date
    Sunday, March 29, 2009 5:33 PM
  • Hi Tech0utsider. Has your issue been resolved? Please respond within 24 hours, or the question will be marked as answered. Thank you.
    • Edited by Adam M MCP Friday, May 29, 2009 12:41 AM
    Thursday, May 28, 2009 2:44 PM
  • Tech0utsider,

    I'm currently running Windows 7 x64 RC, and with a supported motherboard, Windows only identifies 3.25 GB of my 4 GB as usable, whereas this memory is detected and used fine under Windows XP and Windows Vista. There are still some kinks in Windows 7's memory model, and I imagine that they'll be ironed out for the final release.
    -Alex
    Thursday, May 28, 2009 4:38 PM
  • Just judging by how Windows 7 reads compared to Windows XP doesn't tell you you have x64 Windows 7. Can you please confirm it really is the x64 version?
    Friday, May 29, 2009 3:03 PM
  • Adam,

    I'm not certain that that was directed at me, but will this image lay any doubts to rest?
    -Alex
    Friday, May 29, 2009 3:53 PM
  • It was for the asker. It just dropped down to below your post with the same statement. Sorry!
    Friday, May 29, 2009 3:55 PM