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Story: The importance of being 64-bit

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Posted by: Jonathan Forster (Tuesday 17 May 2005, 2:15 AM)

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In your article "The importance of being 64-bit"

So what is all the fuss about, exactly? Technically speaking, a 64-bit chip is one that has integer registers that are 64 bits wide, allowing them to process 64 bits at a time. CPUs store the address of locations in virtual memory in integer registers. This means that the total amount of data the CPU can keep in its working area is determined by how wide these integer registers are.

Which isn't the case for the CPUs you are talking about. The X86 64 bit CPUs still have 32 bit integers. They have 64 bits of address space but the default integer word size is still 32 bits -- that's why it only increased the die size of AMD's original chip by something like 7%. If it really had a 64 bit integer word size the chip would have nearly doubled in size.

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