Both of these articles are full of senseless drivel, particularly the WIki article that describes the 6809 as an "arguably" 16-bit CPU.

I've had many unpleasant experiences with the ultra-slow 6809. It's got a nice instruction set but, if you'll note, it has no descendants. The implementation is about the worst ever done and yet successfully brought to market.

Every Motorola CPU with the exception of the 6804 and 6805 has had at least one 16-bit index register, and those also had A and B registers which could be concatenated into a D register of 16 bits.

The 6809 was a "flash in the pan" made mainly to compete for the IBM application, for which it was considered (I still have one of the original prototypes ... somewhere ...) but which was almost immediately discarded for its weaknesses.

The thing was developed at a time when single-chippers were taking over the microcomputer market, at least the high-volume part of it. The 6801, 6805, 68HC11, 68HC05, etc, took over the Motorola part of that market. Intel did a job in that realm also, as did Zilog, NSC, et. al.

The HC11's that I use now, when the occasion arises, have a demultiplexed bus and operate at 4 MHz. That's not 4 MHz like the 6809, which operates at 1 MHz from a 4 MHz clock, but, rather, at a 4 MHz internal clock. They have several ports, both serial and parallel, and analog I/O as well.

It might interest you to know that, just this week, I put a boxed RS CoCo complete with everything RS provided, in the trash to have it out of my hair. That IBM prototype with the 6809 will go too, next time I run into it.

I mention this only so you'll know I'm not working from a point of complete ignorance, as I investigated nearly every CPU as it became available.

RE