I'm currently running in windows XP 32bit mode with the PAE feature turned on. I have 8GB of Ram installed, but Windows only recognizes 3GB (which is to be expected). I am currently rendering some video, and Windows Task Manager is telling me that I am using 4.75GB of RAM (PF Usage). What is the explanation for this? I would expect the RAM usage to stop somewhere just above 3GB (I have two video cards (512 & 256).
Windows will use/see you pagefile.sys also as 'memory'. You page file is probably 4.80GB, so 4.80 + 3.25 = 8GB memory in total. It is not real memory of course, but it is used as memory.
This link describes how it works.
Video cards are irrelevant to how much RAM you have installed. Irrespective of the size of any page file, if you have 8GB installed;
- Windows 32-bit will recognise upto 4GB RAM
- Windows 64-bit will recognise 8GB+ RAM
Here is an interesting quote about Page files, which seems to make sense considering the size of your pagefile and that your running Windows XP 32-bit;
By default, XP creates a page file which is 1.5 times the amount of installed RAM and places it on the hard drive where XP is installed.
Virtual memory and pagefile are technologies used by Windows to manage memory.
RAM and pagefile appears to the Windows as Virtual memory, so in your case, total amount of usable virtual memory would be 3GB(since 32x bit XP recognizes only ~3GB) + pagefile size (recommended size of PF is 1.5*RAM).