The amount of memory your OS appropriates depends on your system's hardware needs among other things. Each system will have different memory needs. Example...if you had an SLI system and added a second video card, your disposable system memory would adjust to compensate for the second video card. I have 4 GB RAM and my system utalizes just over 3 GBs. You will need a 64 bit OS to recognize and appropriate 4 GBs of RAM. BTW, your 32 bit OS system will still use the 4 GB RAM is it is accessed during use of an appliacation.
 

Losus_Deliosus

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Sounds like you have two 8800GTS640MB in SLI. Much of the hardware in your computer (including video cards and their memory) need to be assigned an address space out of the one big block of addresses your OS handles. If you are running on 32bit version of Vista there is only 32bits worth of address space to assign to all the hardware memory spaces, including your video cards ram and your system ram. In your case your video card drivers are stealing the addressable space just before the 4GB point (Limitation of a purely 32bit OS) to assign to the video card memory effectively leaving a smaller chunk of addresses Windows can use to address to the 4GB worth of main system memory.
 

Losus_Deliosus

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Very odd, that should have left you with 3.25GB of addressable memory, not 2.8GB. In that case I am a little stumped. Do you have any other significant hardware in your computer that would be stealing addressable memory?
 

kuliddar

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Mine is a little over 3gb. What happens to my extra 1gb? Only Vista uses it or is it lost and wasted money? (Running at 32bits as well).
 

Mondoman

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32-bit Vista won't be able to use it either. To use it, you need a 64-bit OS, a MB chipset that can take up to 8GB or more of RAM, and a memory remapping feature in your BIOS.

 

kuliddar

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You know, after carefully selecting the type of computer I wanted, I never thought about RAM limitations in this day and age. Talk about wasted money :(

Having then "too much" : would it do a reverse effect on performance; slowing it down? Should I that 1gb out for now?
 
It's still better to have the use of the extra gig, in Vista at least, XP needs less (and I've heard some ppl say XP can slow down if you have more than 2 gig?)

Anyway, I get 2.9. out of my 4 gig in 32 bit Vista and XP. I've got an 8800 gts (640) but you're not the only one getting 2.8, I've seen that number mentioned here at least a few times on this topic
 
I may be off, But w/ 4G; XP max avail for programs is approx 3.6 Gig, with Vista it's 3.12 (or 3.25).

32 Bit systems use a reserved space for mapping Hardware. When Less than 4 gigs of Memory is installed this space is mapped to virtual memory - Reason that 2Gigs installed still shows 2 Gigs available for programs - Turn of Virtual memory and your avail memory will decreas.

Since 32 Bit can only addres 4 Gigs - The reserved memory now is mapped to the top of the 4 Gigs of real memory

The Less than 3.6 /3.12 has already been covered very well by previous posts
 

Mondoman

Splendid

It depends on the specific hardware installed. For example, someone with multiple cards installed might have less than 3G usable physical RAM under XP.


Exactly! But it has nothing to do with virtual memory. It's just that there are only 4GB of possible memory addresses, and with hardware being mapped into (and thus taking up) some of that space, less than 4GB are left to assign to physical memory. Since hardware never takes up more than 2GB of these addresses, there are always at least 2GB of free addresses for RAM, so no problem with 2GB of installed RAM.

 
Mondoman:
Memory-Mapped I/O (MMIO), for example (Not limited to) video memory must be mapped within the first 4 Gigs of memory. In systems with less than 4 Gigs of physical memory this MMIO is placed in the virtual memory, But when 4 gigs of physical memory is used, it then must resided in that 4 gigs.

Vista (32 Bit) places a limit on grogram memory at 3.12 Gigs, UNLESS the BIOS support Memory remapping.

Reference Support.microsoft.com/kb/929605
 

dengamle

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You have virtual memory and you have physical memory.

So calling MMIO for virtual memory might be confusing, because this has little to do with the memory space where applications live. MMIO has to do with physical memory