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Why is it that 32bit Windows XP can only address 3GB
Windows XP and RAM 3.5GB+
I've seen occasional references that claimed a graphics card's video memory was part of Windows XP's memory address space - is that true? If you have 4GB on an XP system, and add a 1GB graphics card, does that mean Windows only has 3GB for programs?
This effect does not only appear with Windows XP, but with any 32-bit operating system. Please take a look at this Microsoft support article.
Yes. The processor needs to be able to address ram on the graphics card as well. In fact, it will probably be considerably less than 3GB of addressable RAM with the graphics card installed. If you're considering something like this, then you need to be looking at an x64 operating system such as Windows XP Professional x64 Edition, Windows Vista x64, or Windows 7 x64.
I believe that things like graphics card RAM are part of the kernel space. If you have a 1GB graphics card, it won't cut into your 2GB limit of normal user space. It did this in early WHQL drivers for Vista, and it was obvious.
Also, "programs" is a misnomer. Each process gets it's own 4GB, and only half of that is available to a regular user-mode application. So every Windows app will get 2GB, by default, in 32bit mode. Graphics card memory isn't included in this.
