BIOS can't see all installed RAM

Hi,

I've 4GB RAM installed on my board (Colorful, Phoenix award BIOS, PCIEX graphic adapter). The BIOS & OS report 3.4GB or so (cpu-z identifies the entire 4GB). I've googled and found there should be a memory remapping option somewhere in the BIOS, but was unable to locate it anywhere on my machine. Any clue will be appreciated.

TIA
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  1. If your OS is 32bit (and I suspect it is) it can't "see" the whole 4GB of RAM because it has a maximum addressable space of 4GB and in it it has to reserve addresses for I/O ports, graphic memory (which I suspect is 512MB in your case), etc.

    During POST you should see the amount of RAM that is reported. Is it 4GB?
    I don't know where you're reading 3.4 in BIOS, and that remapping option, even if it exists, I don't know how beneficial it is.

    Anyway, I have 4GB of RAM. In Windows XP 32bit I see 3.5GB, and in Windows 7 64bit I see 4GB. In both cases, I think it is more than enough memory.
  2. forever, I believe the mem remapping was an option on some older BIOSs, not seen that much now. I believe that dropping Win 95/98 support made it un-needed, but not sure.

    As PaCanc said, the BIOS should be showing the full 4GBs. As should the info on the POST when the computer boots. It's only 32-bit Windows that will only see 3.4 or so. It's the limit of addressable RAM allowed by 32-bit OS.

    So you're just fine and enjoying all the RAM you can. And your money for 4GBs isn't wasted - your system runs much faster than if you had 2GBs and 3GBs would be slower due to losing dual-channel memory mode.
  3. Hi folks,

    Thank you for answering. My graphic adapter has 1GB RAM, and the exact amount of memory reported by the BIOS after POST is 3406784K. I use 32bit Ubuntu 9.04 which reports 3.2GB. Would switching to 64bit OS let me use the entire 4G's? Not that it's critical - I can live with those 3G+, but still...

    Actually, all I have to do is download Ubuntu 64 Live CD and test it. Will report here when I'm done.
  4. What motherboard/chipset do you have? It might not even be possible to use all of it with a 64bit OS. Linux has PAE support, so you can also address >4G with your 32bit Linux.
  5. I'd say its the OS, but the fact the BIOS reports 3.4 worries me...
  6. I'm with you gamerk - if the BIOS/POST is really reporting 3.4 then there's an issue.

    forever - you said "memory reported by the BIOS after POST is 3406784K". Do you mean that this is the max count displayed by the memory test during POST? Did you enter the BIOS and see this number? Or is this a number reported by some program within Windows?
  7. Yes, this number is what the BIOS displays during POST, right before it scans the HDD controllers and the attached drives.
  8. See my post above. Otherwise everything from here will be guesswork
  9. mikrev007 said:
    What motherboard/chipset do you have? It might not even be possible to use all of it with a 64bit OS. Linux has PAE support, so you can also address >4G with your 32bit Linux.

    The board is a Colorful C.P31AK 2.0 1005 (http://en.colorful.cn/Product/Specific.aspx?guid=f316ccff-23f5-47c2-a468-b36b83c86561). However, just tried this: I disabled Quick POST in BIOS and let him actually count installed RAM. It ran for a few minutes, and reboots when the count reaches 2089xxxKB. Could it be bad memory chip? I don't recall having crashes during heavy memory usage (I ran a game that consumes more then 2GB).
  10. Ah, a Chinese board - never seen it before.

    They don't have a manual available to download, which pretty well kills our ability to walk you thru the BIOS.

    Might recommend using a memory test on it, requires you to make a floppy disk or a CD. memtest86 is a good one. Won't change anything about how much RAM is showing but will make sure it all works.

    If Windows XP reports over 3GBs of RAM, you should be in fine shape. go to Control Panel / System and read what it reports.
  11. memtest86 reports 3327MB, all tests passed with no errors. Windows Vista Ultimate (32bit) says I have 4GB, Ubuntu says 3.2GB. WTH?
  12. I think you're fine. Windows is reporting the correct RAM.

    You might do some more digging into the BIOS to look for memory mapping options. That's about my only suggestion.
  13. Mongox said:
    I think you're fine. Windows is reporting the correct RAM.

    You might do some more digging into the BIOS to look for memory mapping options. That's about my only suggestion.


    Yes, that's what I was trying to find in the first place - the right BIOS setting :D

    I did another test, this time with Win7RC which says: 4GB installed, 3.25GB available.

    Is it possible my BIOS doesn't have any memory mapping option?

    And why POST crashes right after counting 2GB of RAM?

    I can live with the situation as it is now, just thought I could use those missing 0.75GB.

    Thanks
  14. Forget about 32-bit and 64-bit OSes for now, that will come later, because if your BIOS says ~3.3GB then that's all your going to get.

    Some things you can try...

    1. Update the BIOS
    2. Try resetting the CMOS.
    3. Try testing each RAM module one at a time, ie only have one module installed.
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