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    I just found the 6809 difficult to program. It had these combination commands that required an extra level of thinking, very much like Data General Assembler where you had to do a couple of commands in parallel. Commented Feb 19, 2018 at 8:45
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    well, for electrical engineering students just learning microcomputer hardware and software and DSP, the 6809 was sexy. it was the first microporicessor CPU with a multiply instruction that i am aware of. and the orthogonal addressing modes with post-increment and pre-decrement were also quite cool. Commented Feb 20, 2018 at 4:44
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    @traal The 68000 was wildly successful. It didn't contribute to Motorola's demise in any way. Commented Feb 20, 2018 at 9:29
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    @Blrfl: I think that's over-simplifying quite a bit. Motorola made some pretty major changes in how the MMU worked in the 68040 vs. 68030. Then they changed things again in the 68060. Yes, it was possible to detect the processor and use code that worked on each. It's still a lot different from Intels where code written for a 386 in 1987 will still work just fine on a 2018 Skylake X. Commented Feb 21, 2018 at 17:25
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    Also to mention that the 6809 architecture has an excellent addressing mode set with a register layout which leads finally to more compact code even the cycle count is sometimes greater for equivalent instructions compared to a 6502. Superior for pointer oriented stuff, OS implementation, common techniques for compiler-based languages (which was one of several design goals of this CPU). Especially for the stack-based programming language like Forth a 6809 was regarded as the ideal choice. Commented Feb 21, 2018 at 23:12