Re: x86_64 virtual memory map

[Bob Zhang]

in fact , there are two factors to affect how much DRAM final user can use .

for example , for HP's this kind of machine , BIOS can support 40-bit
size and 44 -bit size.
if in BIOS ,user select 44-bit size , then every CPU(socket) can
support 512GB , if user install 8 CPU(socket) , it totally support
4TB.
if in BIOS ,user select 40-bit size , then every CPU(socket) only can
support 128GB , so if user install 8s(socket) , it totally only can
support 1TB, if 4s, only support totally 512GB.

certainly ,this is also decided by OS support 44-bit size or not. if
OS,i.e. rhel5.x  , only support 40bit ,though BIOS 44-bit selected ,
only 40-bit size support every CPU(socket).
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