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Re: significance of bits



On Tue, Jun 01, 1999 at 04:23:59PM -0700, Sudhakar Chandrasekharan wrote:
> Arun Sharma proclaimed:
> > In contemporary microprocessor architecture, the bitness of a CPU is
> > defined by the number of bits in the virtual address i.e. ability to
> > address a large amount of memory in one process/address space.
> 
> I thought that the bitness of a processor was the size of the registers in
> the processor or the width of the data bus.  At least that is what I
> remember (I might be wrong) the Goankar microprocessor text book as saying.

Consider the book to be obsolete. Pentium III is regarded as a 32 bit
microprocessor, even though it has some 128 bit registers, which can
manipulate 128 bits at a time. The data bus is 64 bit wide, address bus
is 36 bit wide.

But Goankar is right in that the general purpose registers on a 32 bit
microprocessor will still be 32 bit (because they're also used for 
addressing virtual memory). But the data bus doesn't have to
be 32 bit.

	-Arun

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