On Thu, 3 Nov 2005, Robert Swier wrote:
>
> No, the 4GB limit comes from the fact that a 32 bit machine names each
> memory location with a string of 32 bits. There are only 2^32 (or
> 4294967296) different bit strings of length 32. So, that is the maximum
> number of memory locations that the system can use in total.
> A 64 bit machine names each memory location with a string of 64 bits, so
> there are 2^64 possible names. 2^64 is practically infinity.
Those are logical addresses that programs use. The memory management units
can map those addresses to a larger physical address which doesn't have to be
limited to 32 bits. Some 32 bit PowerPC's have been doing this for years.
-mark
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