I've Lost My Memory

[lb1947]

From the git-go let me acknowledge that I KNOW this issue pertains to software not hardware, but I'm guessing some of you experts out there could explain why I'm seeing what I'm seeing.

In a nutshell, I have a 1GB memory module installed in each of the 4 memory slots available on my motherboard -- see this post's signature for the complete specs of my computer. But once my Operating System (Win XP Pro SP2 32-bit) takes over after a bootup, the OS sees barely more than 3 GB of memory. And the difference in the amount of memory seen by the OS is minuscule between having 3GB of memory installed and 4GB installed.

I know that, due to limitations of Windows 32-bit operating systems, they cannot address a full 4GB (you can't put an address referencing location 4,000,000,000 in a 32-bit register). I've heard that some motherboards carve out an upper portion of RAM for their PCI-E controllers though I do not know if mine does this or not. So I don't expect the OS to report that a full 4 GB of RAM is available. What I don't understand is why the OS's report of the memory environment when only 3 GB RAM is almost the same as when 4 GB are installed. I've done a quick scan of the web for an answer and was surprised to find that there is a lot of theory and conjecture about this, but no definitive answer as to exactly how much memory a Windows 32-bit OS can address, and how much of that addressable memory is taken up by OS overhead.

My questions are:
(1) Can anyone provide feedback to the situation described?
and
(2) If it turns out that my PC is getting the most use it's going to get of the RAM installed, should I just remove one of the 1 GB memory modules and store it away in case one of the 3 remaining 1 GB memory modules goes bad and I need a replacement?

I could find references to the state of my PC's memory situation in 4 different places:
(1) the General tab when 'System' in the Control Panel is opened;
(2) the 'Performance' tab of the 'Task Manager';
(3) the report provided by the 'System Information' tool located in the START/Programs/Accessories/System Tools menu
(4) the POST when the computer starts up.

I've attached a spreadsheet detailing what each of those 4 report.

As you can see, there is very little difference between having three 1 GB memory modules installed compared to when there are four 1 GB memory modules installed. That makes me think that only a small portion the 4th memory module gets used.

Thanks for any insight anyone can provide.

[Chike]

Re: I've Lost My Memory

It's seems like only a small portion of the 4th 1GB is being used where in fact it is half.
If you remove 1 GB of ram 1GB address space will operate as single channel with somewhat reduced performance.

[lb1947]

Re: I've Lost My Memory

Chike:
Good point. I guess leaving the 4th memory module in helps a little. Thanks for your reply.

[pbcopter]

Re: I've Lost My Memory

With Windows x86 (32 bit) all it can address is 4GB of space. Whether that space contains memory (RAM) or other hardware. So if you put in 4 GB of RAM, it will address all (about 3.25 GB) but what is needed for the other resources (hardware). If you only put in 3GB, then it will address all of it since the remaining 1gb of address space can be used for the other hardware.

BTW, I lost most of my memory years ago I think, I can't remember ;-)

[profJim]

Re: I've Lost My Memory

FWIW, I've superimposed my w2k (32-bit) results over your document.
With 4GB of memory, my swap-file usage is much lower than if I run with 2GB of memory.

Keep in mind that 3,668,396 divided by 1024 = ~ 3,582.4 MB or ~3.498 GB.
My system is running with a 1GB swap-file.

You haven't lost your memory, it's just hard to find.