Re: What is an N-bit machine?

Anton Ertl <anton@mips.complang.tuwien.ac.at> schrieb:

In the early 1980s the width of the data bus of the main
implementation of an architecture was considered to be defining the
bitness of the architecture.  This is especially noticable in the
68000, which was usually described as 16-bit CPU, despite having
32-bit address and 32-bit data registers, because it has a 16-bit data
bus.  I think that even Motorola called it a 16-bit CPU. With low-cost
variants such as the 8088, the 68008, and later the 386SX, that idea
was not kept up.

It had been my impression that the width of the ALU was the
definition for many computers - the widest integer that can
natively be handled.  (That does not really fit for the low-end
/360, but that was a 32-bit architecture, and worked for the mid-
and high-end machines).  The 68000 was indeed advertised as a
16-bit processor, the 68008 also had a 16-bit ALU.

The original Nova with its 4-bit ALU does not really fit, I
think Edson de Castro quipped was that it was a 4-bit computer
masquerading as a 16-bit computer. (They later introduced
real 16-bit computers).

Notable counterexamples? (OK, the PDP-8/S :-)