On 13/03/2008, Apptech <apptech@paradise.net.nz> wrote:
> Well, that's (embedded) news to me!
>  I'll have to look. What did I say ? :-)
>
>  I assume that's related to the smallest bus width computer
>  ever (MC14500). No?

Spot on!

Here you go...

"Russell McMahon submitted: The all time most terrible and narrowest
bus width "microprocessor", assuming such an exalted title dare be
applied, and assuming that there has never been a none-bit processor,
although any number of mine have assumed that apparent state over the
decades, was the dread Motorola 14500 "1 bit" microprocessor.

A perfunctory web search, employing effort worthy of such a device,
turns up a number of references but neither data sheet, nor seller
willing to admit stocking them.

>From memory they achieved their claim to 1 bit status fame by having
an execution unit which returned a binary true/false when various (and
necessarily limited) tests and operations were carried out. Presumably
(and memory dimly suggests) the obvious AND/OR/XOR and I seem to
recall a TAD or ADD. The outcome of a test would enable or disable the
execution of subsequently fetched instructions and the device would
chug oh so slowly up its memory until some text condition was met,
whereupon the instruction decoding was reenabled and execution
recommenced. All program locations were ALWAYS accessed sequentially
as an endless loop with program flow including any conditional jumps
being achieved by turning off execution, meandering through address
space and then reenabling execution when the relevant test of
condition produced a true result.

>From dim recollection, the title "1-bit" was a misnomer as you
effectively built tests of a width that suited externally using such
hardware as requisite."

Dan
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