A question about IA32 architecture

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fbiyuwei
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A question about IA32 architecture

Post by fbiyuwei »

Hello everyone，I have studied IA32 architecture since a week ago.In many books ,writers always said:"In page mode,you can access memory more than 4GB."It always makes me very puzzled，please tell me why can a 32-bit CPU access memory more than 4GB in page mode!
Thanks for your answers!
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Rusky
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Re: A question about IA32 architecture

Post by Rusky »

You may be talking about PAE, or physical address extensions. This makes the physical addresses in page tables big enough to access more than 32 bits, while virtual addresses remain the same size. Individual processes still only see a 32-bit address space, but multiple processes combined can access more.
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Combuster
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Re: A question about IA32 architecture

Post by Combuster »

There's also PSE36 which works as a drop-in hack for old paging users, but the net effect is the same: You can point to anywhere in 64GB but only use 4G of it per address space.
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