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On 10/09/2013 05:17 AM, gottlieb@×××.edu wrote: |
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> On Tue, Oct 08 2013, Alan McKinnon wrote: |
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> |
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>> That is correct, with 3G physica RAM, you will not benefit from using |
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>> PAE at all. I don't think it interferes with anything if you do have it, |
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>> I recall a time when RedHat shipped 32 bit kernels that were PAE-enabled. |
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>> |
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>> Briefly, the way it works is that the kernel assigns blocks of memory to |
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>> different processes. So a single process can still only access 4G of |
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>> memory, but two different process don't anymore have to address the same |
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>> 4G of memory like you must do without PAE. But you still don't get to |
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>> give your 32 bit database more than 4g of RAM |
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> Agreed. Virtual addresses refer to those in the program (really |
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> process). Physical addresses address refer to those in the hardware |
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> (i.e. addresses in the RAM itself). To have a single process able to |
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> access extra memory would be to increase the *virtual* address range. |
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> PAE (*physical* address extension) enables more RAM to be accessed (by |
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> the hardware not by a single process), but does not increase the virtual |
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> address range. |
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> |
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> When pdp-11s added I and D space, that increased the virtual address |
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> range by a factor of two. The I/D bit (instruction/data) was |
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> essentially an extra bit of virtual address. |
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> |
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> allan |
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> |
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Thanks a lot for the explanation. Much appreciated. |
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