32 bit and more than 4 gb memory on servers

enkidoe

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Jan 27, 2009
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guys,

In the past, we had 32 bt servers with more than 4 gb memory. how did that work? Anyone who remembers that?

thanks
 
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Nukemaster is correct.

The technology is called Physical Address Extension. This allows a platform to have more than 4GiB of physical memory but each individual process will still be limited to 4GiB including system memory and memory-mapped IO.

32 bit versions of Windows will enable PAE by default where the NX bit is supported (Pentium 4 Prescott microarchitecture if I recall correctly) starting with Windows XP SP2 which introduced OS level support for the NX bit. On 32-bit client versions of Windows (Windows 2000, Windows XP, Windows Vista, Windows 7, Windows 8, and Windows 8.1) the total address space size is still limited to 4GiB (mostly for marketing reasons) even if PAE is enabled. There are some unsupported kernel hacks which can be used to disable this limit. In fact, 32-bit versions of Windows 8 and Windows 8.1 only have a PAE kernel and the microprocessor must support the both PAE and the NX bit. Server versions of Windows (Windows 2000 Server, Windows Server 2003, Windows Server 2003 R2, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2) are not affected by the 4GiB limitation when PAE is enabled.
 
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