4gb ram on 32bit machine?

[JXY]

Hi,

I'm running 32-bit XP Pro Sp3, and recently i installed two 2gb kingston notebook ram cards for my HP pavilion dv2600 laptop. However, my machine tells me i've only got 3 gb of RAM. This is checked with everest. However, CPU-Z says i've got 4 gb.

my question is, why does my computer only "see" 3gb?

if it's due to the fact that i'm running 32-bit version of XP and not 64-bit, then is the additional 1gb of RAM in use by my machine?

[Doomsayer]

Well,  32bit windows should support up to 4 Gb of system memory.  since a 32 bit machine means that the processor can access a memory address up to 32 bits long. this is 4.2 billion unique memory addresses or 4 Gb of memory.  so in 32 bit windows There is an imaginary 4.2 billion unique addresses available to applications.   (I think I explained this right)

This means that while we can't say it's not window's fault that your computer isn't recognizing the last Gig.  It is very capable of supporting 4 Gb.  the problem I would guess is likely hardware.  Look up your motherboard model online and see how much RAM it can support,  Since the buses and physical design of a motherboard can physically limit the amount of system memory capable of being used.

good luck

[Dias de verano]

This old favourite keeps coming up. There ought to be an FAQ about it. It's not really to do with hardware as Doomsayer seems to think. No hardware will enable 32 bit Windows to see 4 GB of RAM.

If you are running 32-bit Windows, you must live with it. You will not ever see all 4GB of RAM you've paid for. Due to an architectural decision made long ago, if you have 4GB of physical RAM installed, Windows is only able to report a portion of the physical 4GB of RAM (ranges from ~2.75GB to 3.5GB depending on the devices installed, motherboard's chipset & BIOS).

This behavior is due to "memory mapped IO reservations". Those reservations overlay the physical address space and mask out those physical addresses so that they cannot be used for working memory. This is independent of the OS running on the machine.

Significant chunks of address space below 4GB (the highest address accessible via 32-bit) get reserved for use by system hardware:

    • BIOS – including ACPI and legacy video support

    • PCI bus including bridges etc.

    • PCI Express support will reserve at least 256MB, up to 768MB depending on graphics card installed memory

What this means is a typical system may see between ~256MB and 1GB of address space below 4GB reserved for hardware use that the OS cannot access. Intel chipset specs are pretty good at explaining what address ranges gets reserved by default and in some cases call out that 1.5GB is always reserved and thus inaccessible to Windows.

[JXY]

oh. so some of the invisible 1g of ram on my machine is added to my graphics memory? improving game performance?

[Dias de verano]

oh. so some of the invisible 1g of ram on my machine is added to my graphics memory? improving game performance?

No. The address space from 4 GB downwards that you cannot use, cannot be used for RAM. Windows uses those addresses for memory mapped system hardware input/output, no matter how much (or how little) RAM you have installed. If you install more than 3 GB of RAM you run into this problem. That part of your RAM is not being used for anything. It might as well not be there.

[JXY]

oh. i see.

thnx for the information :p

JXY

[Spoiler]

Some more reading and stuff on this....

http://members.shaw.ca/bsanders/WindowsGeneralWeb/RAMVirtualMemoryPageFileEtc.htm

[JXY]

k.  appreciate the source.