Rev. Layle said:
I'm curious how that works, if the OS can only physically address 3.2 GB (assuming that is what is being reported), how is the extra memory addressed if device I/O is mapped there instead?
(serious question, not trying to be snarky)
The OS actually maps 4GB of
address space
The system, your video card, or any other device with onboard memory, eats into that. Typical computers will see 3.2GB. Because I have TWO video cards, for example, mine only sees 2.8GB+-
If i SLI'ed 3 video cards at 512mb each I would only get 2.2GB. See how that works?
Remember, the Video Card in modern systems is not so much for the extra memory, but more for the dedicated GPU and (typically) faster GDDR3 or GDDR4 RAM. Also, Vista 32 can actually see all 4gb, even though it only uses 2.8gb of it in my case. The main reason I went for my config is overclocking. Just easier to find settings for 2 DIMMS of 2gb corsair dominator. By the way, I'm not an OC expert, so I may be wrong on this last part, but I believe timings are weird on odd #s of
dual channel RAM.
With the new Intel I7 processors and mobos with tri-channel RAM, the same will be said for even # of DIMMS installed. The I7 is probably a waste for most people though. 8 Logical Cores is useless to 99.99999% of people unless they do some hardcore multitasking. For today's multi-tasking environment I think Quad is all ya really need. The real reason to get an I7 is the tri-channel memory and the integrated memory controller (huge thing). That got rid of a gigantic bottleneck that Intel was suffering from on their chips. Also, I believe the four cores of the I7 are on one die.
Well that was a bit of a rant. TL;DR / Getting straight to your question:
The OS has 4gb of address space. Before you get to use anything all installed devices, the system, and even windows itself will eat a chunk of your RAM. Don't get confused by FREE showing almost 0 in vista though. All that "cached" stuff is actually usable by any program