On Fri, Apr 3, 2009 at 1:51 PM, Juned Shaikh <jsha...@gmail.com> wrote: > but I am wondering that why would you need to have PAE in win2k8? becuase > you have 32 bit installation or you need this on Win2k8-64 Bit for 32 bit > enabled > applications?
PAE will let some versions of 32-bit Windows use more than 4 GiB of RAM. Individual processes are still limited to 2 GiB of userland address space (or 3 GiB with 4GT), but the system as a whole can use that much RAM. You could, for example, have several processes, each using 2 GiB. PAE is also needed to get the NX bit (No Execute, i.e., what Microsoft calls Data Execution Protection). So even 32-bit XP and Vista enable PAE for DEP. They just ignore memory above 4 GiB. Same for 2003 Server Standard. On Fri, Apr 3, 2009 at 1:52 PM, Michael B. Smith <mich...@owa.smithcons.com> wrote: > if you are running 32-bit or if you are running 32-bit emulation in 64-bit > (i.e., > running 32bit SQL server on 64bit windows). I don't think the concept of PAE exists in long mode. The processor and OS are already using a 64-bit word for both physical and virtual addresses, so what's the point? There are still only 36 address lines coming out of the processor, of course, but that's an implementation detail that's not visible to the software. Meanwhile, PAE never meant anything to 32-bit userland software. Win32 processes were still limited to a 32-bit virtual address space. Under Win64, they'll be given a 2 GiB userland by default, or 4 GiB if they're LARGE_ADDRESS_AWARE. If they want to use AWE (Address Windowing Extensions, Microsoft's name for bank switching), they can, but AWE is an OS API feature, and doesn't affect the virtual address space of the process. -- Ben ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
