Re: Identifying CPU and current OS
At Mon, 29 Sep 2025 12:28:37 -0400 Dan Purgert <dan@djph.net> wrote:
>
> On Sep 29, 2025, Greg wrote:
> >On 2025-09-29, Michael Stone <mstone@debian.org> wrote:
> >> On Mon, Sep 29, 2025 at 05:26:54AM -0500, Richard Owlett wrote:
> >>>Underlying my question was the assumption that when a processor was
> >>>referred to as 32 or 64 bit, it was a reference to the width of the
> >>>data bus.
> >>
> >> Not really, which is why this was a weird/misleading/confusing question.
> >> A "bus" is the physical connection between components in a computer. The
> >> (basically obsolete) phrase "data bus" referred to the physical
> >> connection between the processor and external components. In early
> >
> >I thought a 32-bit data bus meant � 4 bytes at once, and 64-bit data bus
> >meant � 8 bytes at once (i.e. the number of bits capable of being
> >transferred over the bus in parallel, simultaneously).
>
> This was true for some period of time; but I think it started becoming
> less true around the days of the 386 or 486, as they were 32-bit
> processors, but many peripherals of the era were still only able to send
> data in 16-bit chunks.
>
> No point in having a 32-bit wide data bus when things like PATA or ISA
> cards were only 16bit max.
>
> I *believe* PCI (and for a time, AGP) were capable of running in 32-bit
> modes, but then they also died off to serial interfaces (PCIe, SATA,
> etc.)
>
> As far as I am aware, the only remaining parallel data bus on a PC is
> the connection to RAM.
I *think* some late i586 or i686 systems while being "32-bit", might have had
64-bit data buses facing RAM (to speed up loading the cache memory). Which
just throws another monkey wrench into the "What is the data bus size?"
qyestion,
>
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