freakwave wrote:Window XP + Windows Vista are limited by Microsoft to not support more than 4Gig. You only see (4Gig - X) because the X is used by PCI devices, that use this Address space.
32 Bit OS is able to easily support more than 32 address lanes, but Microsoft does set the limits.
You are referring to Intel's Physical Address Extension (PAE) ... basically this is like the 8086/8088 segment registers on steroids. Not a nice linear address space, and generally not easy to manage. Windows 2003 R2EE does do this, and hides the complexity from applications, but it's by no means trivial.
Or maybe you could suggest some other OS examples where PAE is available -- and was easily implemented! -- and the additional memory is simply and easily accessible to applications?
The reality is that it's an abomination, just like the original segment registers (which were abhorrent compared to the 68000's linear 32-bit address space and symmetric register set). Otherwise Intel wouldn't have eaten humble pie and adopted the AMD64 instruction set for the Core 2 processors ...