Virtual memory size and allocation -

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on 32-bit x86 systems, total virtual address space has theoretical maximum of 4 gb. default, windows allocates half address space (the lower half of 4-gb virtual address space, x00000000 through x7fffffff) processes unique private storage , uses other half (the upper half, addresses x80000000 through xffffffff) own protected operating system memory utilization.

64-bit windows provides larger address space processes: 7152 gb on ia-64 systems , 8192 gb on x64 systems.

i have several questions above quote :

  1. why low address space allocated processes?
  2. "...uses other half (the upper half, addresses x80000000 through xffffffff) own protected operating system memory utilization." - why operating system doesn`t use physical addresses system address space,but uses virtual addresses?
  3. why on x64 system 8192gb used process , system?in oppose 32bit os not space of addresses used?

thank you


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