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I understand the 32 bit Vista limit in addressing only 4Gb of memory space but I have a very specific question:

I have 3Gb installed on a Vista 32 bit system with a 512Mb video card, MSI X-58 board, Intel i7, 920 CPU. System Information currently shows: Installed Memory: 3.00Gb Available Physical Memory: 1.73 Gb

My understanding is that the 512Mb video card occupies memory addresses between 4.0Gb and 3.5Gb and so does not subtract from the 3.0Gb of physical memory (correct my understanding if wrong)

My Question: If I install another 1Gb of RAM, will my Available Memory increase to 2.73Gb?

Thanks, Bob423

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Is the video card shared memory? If so it is subtracted from physical memory. But even if so, I cannot see you come from 3GB installed to 1.7GB available memory... there are nearly 1GB missing. –  Felix Dec 14 '09 at 23:17
    
The Avaiable Memory number of 1.73 GB comes directly off the System Information summary page. Installed Physical Memory (RAM) 3.00GB Total Physical Memory 2.99 GB Available Physical Memory 1.73 GB Total Virtual Memory 6.90 GB Available Virtual Memory 5.63 GB Page File Space 4.00 GB Yes, I was puzzled by the low number. I was expecting a little under 3.0GB. I thought adding 1GB RAM would help or else there's something else wrong with my system. Bob 423 –  user21426 Dec 15 '09 at 0:47
    
My video card is ATI 4850 with 512Mb. –  user21426 Dec 15 '09 at 0:50
    
It's not just the video card using that "unusable" RAM. There's other devices on your machine. That said, you might be able to get up to 3GB usable by going up to 4GB. The only way to check is to actually try it. –  user3463 Dec 15 '09 at 7:52
    
Hi Randolph, Yes, I'll buy the RAM today and give it a try. I was wondering if anyone had tried the 3Gb to 4Gb upgrade and knew the results. –  user21426 Dec 15 '09 at 12:55
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Your comment describes it perfectly (I've reformatted & corrected the one typo):

The Available Memory number of 1.73 GB comes directly off the System Information summary page.

Installed Physical Memory (RAM) 3.00GB
Total Physical Memory 2.99 GB
Available Physical Memory 1.73 GB
Total Virtual Memory 6.90 GB
Available Virtual Memory 5.63 GB
Page File Space 4.00 GB

Yes, I was puzzled by the low number. I was expecting a little under 3.0GB.

The "Available Physical Memory" isn't what your system is able to access, it's what's left after everything running has its memory allocated. Every running program and service eats up some memory, so this seems perfectly normal to me (especially since Vista's memory footprint is fairly large).

Your system recognizes its full 3 GB of RAM. But it has to allocate for all your running software. This value will fluctuate depending on exactly what your machine is running at any given moment, and even what those particular apps are doing.

If you add a 1GB chip, you'll probably see between 256 and 512 meg additional, depending on all of the various hardware resources in the machine, in a 32-bit environment. In a 64-bit environment, you would see the whole GB. However, this will be shown as installed and total physical memory -- not necessarily as "available" physical memory, as again, that value fluctuates depending on what your machine is doing.

In any event, you should note that under normal circumstances in a 32-bit environment, most apps will not be (individually) able to use more than 2GB at a time. However, for the vast majority of end users, this should not be an issue.

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John, thanks for the advice. I ordered 6Gb (2Gb x 3) for my system and I'll see what happens to available memory - I'll post my results here. Today, I ordered Windows 7 64 bit and I'll install that too and report back, ought to be fun doing a clean install. –  user21426 Dec 16 '09 at 1:58
    
Well, I just installed three sticks of 2Gb RAM (Corsair XMS3, TR3X6G1600C8 G) in preparation for installing 64 bit Windows 7 in a few days. First I wanted to check on what System Information reported. Installed Physical Memory (RAM) = 4.00GB Total Physical Memory = 2.99GB Available Physical Memory = 1.84GB I suppose the installed physical memory number is only 4Gb since that's what a 32 bit system can see. However, I'm very puzzled by getting the same number as before for Total Physical Memory (2.99GB) and the measely increase from 1.73 to 1.84GB! Does anyone know what is happening? –  user21426 Dec 20 '09 at 2:18
    
Available, again, is going to fluctuate based on the system. In terms of what's visible, there's 4GB of addressable space altogether -- that means that every device that requires memory mapping (video, sound, certain types of storage, etc) gets a chunk of the 4GB before you get at it. It's also possible that your motherboard doesn't fully support the RAM. Bottom line: Once you get to 4GB, you usually should switch to 64-bit unless there's a very compelling reason to remain 32. –  John Rudy Dec 20 '09 at 18:05
    
The saga continues! I replugged the first stick and got the installed physical memory to read 6GB! I thought I would run CPU-Z to take a look at the memory and got a great surprise. CPU-Z identified one of the sticks as manufactured by SuperTek. The other two were by Corsair. All three were labeled as Corsair XMP-1600. Furthermore, the SuperTek stick was not ID'ed as 1600 capable by CPU-Z. Strange, strange. I RMA'd all the RAM back to Newegg who's accepting all of it back at no charge and also paying for the postage (kudos to Newegg!!) –  user21426 Dec 21 '09 at 2:01
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You can read this blog entry. It contains useful information on what memory the system is seeing.

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