> I heard that the IBM 709
> series had 36 bit words because Arthur Samuel,
> then at IBM, needed 32 bits to identify the playable squares on a
> checkerboard, plus some bits for color and kinged

To be precise, Samuel's checkers program was written for
the 701, which originated the architecture that the 709 inherited.

Note that IBM punched cards had 72 data columns plus 8
columns typically dedicated to sequence numbers. 700-series
machines supported binary IO encoded two words per row, 12
rows per card--a perfect fit to established technology. (I do
not know whether the fit was deliberate or accidental.)

As to where the byte came from, it was christened for the IBM
Stretch, aka 7020. The machine was bit-addressed and the width
of a byte was variable. Multidimensional arrays of packed bytes
could be streamed at blinding speeds. Eight bits, which synced
well with the 7020's 64-bit words, was standardized in the 360
series. The term "byte" was not used in connection with
700-series machines.

Doug