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Unable to see all 4 gigs of ram in vista 32 bit. please help

Last response: in Windows Vista
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March 21, 2007 2:53:42 PM

So I've been reading and everyone is saying that vista 32 allows up to 4 gigs of memory, well i have 4 gigs of ram the bios states that its 4 gigs. Windows displays it as 2.75 gigs. i do have a 256 meg video card. is there a command i can run that will let windows see 4 gigs of ram? OR does anyone know if windows is using all of my ram, if so i dont care what windows says.
March 21, 2007 8:24:11 PM

A 32-bit OS can only address 4GB total. Vista (and XP for that matter) and general system resources will tie up 1 - 1.5GB of address space, so the maximum RAM a 32-bit system will be able to utilize is between 2.5 and 3GB. To be able to utilize 3GB or more of RAM, you need a 64-bit version of Windows.
March 21, 2007 8:48:08 PM

so the 4 gigs i have 2.75 is being displayed.. is the other 1.25 being used at all.. am i benifiting from that 1.25 gigs in any way. im kin of foggy, are you saying that the 1.25 is being used by backround stuff..
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March 21, 2007 9:22:22 PM

It's all about address space, not just RAM size. Every component (vid card, sound, motherboard controller chips, etc) in a system takes a block of addresses, as well as some overhead addresses for Windows to be able to operate.

A 32-bit OS can only "see" 2^32 = 4,294,967,296 (4GB). Since your system is using about 1.25GB worth of address space (not including your RAM), there is only about 2.75GB worth of addresses to be assigned to your RAM. So, to answer your question - the extra 1.25GB of RAM that you have that Windows can't see - is not being used at all as there are no address spaces left to assign to it. Without an address, Windows can't see it - let alone use it.

A 64-bit OS is 2^64 = 18,446,744,073,709,551,616 (18 Exabytes). This is the theoretical limit for a 64-bit OS. It's theoretical, as nobody is going to make anything with 18 Exabytes worth of trace lines. Most Mobos are limited to 4-8GB of RAM- probably will increase soon, but not to 18 Exabytes.

If you're interested, here is a brief Wiki article on address space:
http://en.wikipedia.org/wiki/Address_space
March 23, 2007 6:04:39 PM

Quote:
are you saying that the 1.25 is being used by backround stuff..

No, it is NOT being used. The addresses are being used by the system, but not the RAM at those addresses. The addresses are used for accessing the PCI devices, the onboard peripherals, and the BIOS itself, etc. The system must address all hardware through addresses, which are assigned at bootup. Once these addresses are assigned, the RAM at those addresses is effectivly hidden and is NOT being used. You need to go to a 64-bit OS to get past this.

Here's a one page document from HP that describes pretty nicely exactly is going on.

Under XP, you could get around it using a "/PAE" switch added to the boot.ini. It got around the hardware addressing scheme by playing around with flipping on and off banks of memory, slowing down memory performances, and therefore overall performance. You got to access all 4GB of your memeory, but the trade off was that you accessed it slowely. I think that switch doesn't even work anymore as of XP's SP2.
March 24, 2007 3:31:54 AM

Your current configuration has to map all of the original, vacant DOS and bios areas into the 1st Meg of memory, as well as the full, real bios (usually above 1M and could be up to 256M) and then as others said, map additonal space for video (could be 512M+its bios) and more for other memory mapped IO devices.

Your system is a little loose, most of the time in a 32-bit system, you wind up with access to 3.25G. For some reason, with your particular MoBo and other hardware requirements, you appear to be losing an additional .5G. You may have some bad memory which the bios would just map out and you wouldn't really know it; you probably should download and run memtest86 (its free) for verification.

If your memory is good, you can pick up the full 4G, if you can get and can run the 64-bit version of Windows (emt64 or amd64). Hey, you get to rationalize some of the money it may cost you as effectively purchasing another 1.25G! You can get Vista 64 with any full copy of Home Premium (need to request a copy from MS) or Ultimate. This will enable the OS to use all 64 address lines and that will allow it to remap your full ram into its active address space.

Joe
March 24, 2007 9:30:19 AM

Quote:
Your system is a little loose, most of the time in a 32-bit system, you wind up with access to 3.25G. For some reason, with your particular MoBo and other hardware requirements, you appear to be losing an additional .5G. You may have some bad memory which the bios would just map out and you wouldn't really know it; you probably should download and run memtest86 (its free) for verification.
Memory is probably fine. I was only able to see 2.8GB on my Asus P5-B Dlx until I went to 64-bit. You might be able to raise the number disabling unused onboard components. i.e., does your MB have to LAN ports but you're only using one? Disable the other in the BIOS. Not using onboard sound or COM or parallel ports? Disable them. Not using SATA or IDE controllers? disable them.
March 26, 2007 3:21:01 AM

Hey,

I am running 64-bit windows, and have installed 4GB of RAM, and myself only have 2.75 GB of RAM showing up and I have run mem test on it multiple times. I am unsure why this is if you say that 18 exabytes could show up on it. If anyone has any ideas as to why this is please let me know. Thanks,

topgunw
March 26, 2007 3:31:02 AM

Quote:
Hey,

I am running 64-bit windows, and have installed 4GB of RAM, and myself only have 2.75 GB of RAM showing up and I have run mem test on it multiple times. I am unsure why this is if you say that 18 exabytes could show up on it. If anyone has any ideas as to why this is please let me know. Thanks,

topgunw


Maybe your MB doesn't support more than 2.75G... You don't tell enough to go with, who makes it?
March 26, 2007 4:05:25 AM

Sorry, I thought I had put that in. I am running a Asus A8N32 Sli Deluxe Gaming Mobo. Seen Here:

http://ca.asus.com/products4.aspx?l1=3&l2=15&l3=226&mod...

I do believe it does say it supports 4GB of RAM.

I also have an AMD 64 FX-60
4GB RAM
2x 7900 GTX not in SLI currently

If you need more info let me know.. thanks for your help though
March 26, 2007 5:24:44 AM

You BIOS might have a "memory mapping" feature that needs to be enabled. Or maybe it's "memory remapping'; i forget. My Asus P5B-Deluxe has this setting which needs to be on for 64-bit Vista to see everything.
March 27, 2007 4:56:28 AM

Asus has a couple of bios updates for that MB that deal directly with reported memory or incorrectly dealing with a 'hole' in memory. Both could be relavent to your problem.
March 28, 2007 7:54:25 PM

According to the articles linked below, on (non-PAE-mode) Vista 32-bit systems there is a limit of 3.12 GB for the available system memory, which is also said to be the amount of system memory typically available.

(The limit is different if PAE-mode is enabled; however, this mode has driver incompatibility issues, among other things.)

Inasmuch as your system is showing only 2.75 GB of available memory, it may either have a configuration that is atypically demanding in terms of memory-mapped I/O devices or other such subtractions from the addressable space below the 4GB limit; or there may be something wrong causing unnecessary hole(s) to be allocated (as was suggested by another poster).

http://support.microsoft.com/kb/929605
http://www.dellcommunity.com/supportforums/board/messag...
March 30, 2007 3:33:38 AM

Thanks guys turning the memory mapping feature on on my mobo allowed it to see all 4GB. ^-^ 64-bit is definitely the way to go
!