knudsen@ihnss.UUCP (02/16/84)
Been a lot of discussion here about honest & correct ways to determine a given micro-proc's "true" wordsize. I submit that the MOST IMPORTANT measure is: (the envelope please): The largest wordsize that the Programmer can THINK in while using this micro. This is directly related to the registers and the ALU, but *not* to the external pinout. For example, the 8086 lets me think in 16-bit terms; I can load, add, and store (even multiply) 16-bit integers. The 8088 appears ientical to the programmer, despite its half-sized data bus, so still deserves to be called a 16-bit machine. Note that allowing a programmer to think in N-bit words means much faster and shorter object code than on an N/2-bit machine. Even tho the 8088 uses extra micro- (and bus) cycles to add a 16-bit word, it beats hell out of a Z80 executing several instructions to do double-precision. So it isn't just programmer convenience I'm thinking of. By this criterion, the 68000 is a 32-bit micro, until you go to multiply. The 6809 is a 16-bit machine for simple arithmetic, but only 8-bit for logical and multiply work. With their floating-point attachments, the 8086/8 and some PDP-11s are 64-bit, since you can treat floats as single entities, and let microcode (ie, hardware) do the work. mike k