installed memory recognized in bios but not in win xp pro

Discussion in 'Hardware' started by chiguy, Dec 14, 2005.

  1. thanks for all your help with my previous i have a new question...

    i installed 4 gb of ram in my machine...

    ibm bios and setup recognizes it...

    win xp pro shows only 2.75 gb of physical memory...

    any ideas ?
  2. XP is a 32 bit operating system and has a constraint on the ammount of physical memory it can report. 3 gigs is the limit. Now dell tells me my computer is able to use the full 4 gigs, but xp only reports and manages 3 gigs....until you want to install xp64 that is it.
  3. skepticaltrader

    skepticaltrader Guest

    I know on some machines that when you install up to 4GB of Ram, the computer will only show 3GB.

    I bought a motherboard awhile back and it says in the operating manual that the computer will only show 3GB instead of the 4GB.
  4. thanks...

    i guess the question is am i getting the use of the unseen ram or is it just sitting doing nothing...

    or is an upgrade in my future....
  5. skepticaltrader

    skepticaltrader Guest

    I would assume that you're getting the full 4GB of RAM. There is no real way to tell though. I doubt mb manufacturers would make a mb with the capability of 4GB of RAM if you couldn't use it.

    You could probably check with some mb manufacturers to see if they have a way to check the physical memory on a computer if there is 4GB of RAM installed.
  6. just found this...

    Here's a list of how much RAM the various Windows versions and editions support (as of Nov 2004):

    Windows NT 4.0: 4 GB
    Windows 2000 Professional: 4 GB
    Windows 2000 Standard Server: 4 GB
    Windows 2000 Advanced Server: 8GB
    Windows 2000 Datacenter Server: 32GB
    Windows XP Professional: 4 GB
    Windows Server 2003 Web Edition: 2 GB
    Windows Server 2003 Standard Edition: 4 GB
    Windows Server 2003 Enterprise Edition: 32 GB
    Windows Server 2003 Datacenter Edition: 64 GB
  7. nitro


    Write a simple C program, allocating 1Mbyte at a time in a for loop, and print out the value of loop index when malloc returns an error. Multiply index * 1Mbyte immediately after the error and that is how much you were able to alllocate and will tell you how much RAM the machine can see.

    Win XP has a footprint of about 500MB. So assuming very little else is running, the index should be about 3500 (equating to 3500 megabytes, or 3.5 GB) before it errors on a 4GB machine. The value of index * 1M when malloc errors is the actual amount of RAM the machine can see.

    It might be a little more complicated than this if you can alloc into paging file. I forget but I think you can control that the memory actually allocates into RAM. Otherwise make the paging file as small as possible and take it into consideration when doing the math.

  8. nitro, you're too funny. :p

    Incidentally, wouldn't memturbo or a similar shareware utility show actual usage?
  9. you could even use tupe up utilities, I think, it has a memory usage, I have 1.5gig of ram and I only use I think 40% when run 3 monitors and x trader, plus sufing the web and skype!