On Fri, Oct 12, 2018 at 07:06 PM, Chuck Harris wrote:
Depends on what you call "substantially similar". Yes, the 6502 derives from the 6800 (6802) but architecturally, it is much simpler (it was developed to save costs against the 6800 with the 6502's deficiencies being called "features" by some). The 6802 had a single supply voltage and a single-phase, like the 6502 and was a more integrated thing than the original 6800.
For starters, the 6502 had a very different programming model with 1 accumulator against the 6800's 2, an 8-bit stack pointer with a hardwired address space vs. the 6800's 16-bit. Obviously, opcodes were different. It had a few advantages as well (as an example, the 6502 had a BCD mode AFAIR).
Many (cross) assemblers can be used for both families with appropriate settings.
In all, it's far less orthogonal than the 6800's architecture but much more so than Intel's 8080 and everything Intel that followed (until today).