At Mon, 29 Sep 2025 12:28:37 -0400 Dan Purgert <[email protected]> wrote:
> > On Sep 29, 2025, Greg wrote: > >On 2025-09-29, Michael Stone <[email protected]> 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 â 4 bytes at once, and 64-bit data bus > >meant â 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, > -- Robert Heller -- Cell: 413-658-7953 GV: 978-633-5364 Deepwoods Software -- Custom Software Services http://www.deepsoft.com/ -- Linux Administration Services [email protected] -- Webhosting Services
