it depends on how many address lines the CPU has. A 32-bit CPU can have 2^32 = 4294967296 addresses. I think.
Looking at new computers with Win XP Pro, they all seem to top out at 2 Gigs of RAM ... even those with 4 DIMM slots. Since 1GB ram sticks are relatively affordable nowadays, I'd like to maximize the capabilities of my next system as much as possible.
Is the amount of addressable memory a limitation of the hardware or the OS ?