65802 vs. 6809 vs. 65816

[KG7PFS]

I once heard that the 6809 was considered the most advanced 8-bit (8/16-bit) CPU ever. I also heard the 65802, available at the same time, wasn't quite as good. Is that true? What is the difference? Other than extended addressing, what's the difference between the 65802 and 65816?

 

[njroadfan]

The 65802 is a 65816 that is pin compatible with a 6502. It doesn't support 24-bit addressing however, so you are limited to 64k of RAM just like the 6502.

 

[commodorejohn]

The 6809 has more registers and more addressing modes than any 6502 variant; in particular, it can do stack-relative addressing easily, which is great for high-level languages and reentrant code.

On the other hand, the 65816 has better 16-bit capabilities and the ability to address more than 64KB of memory. The 65802 is just a 65816 in a 65C02-compatible package, meaning it can only address 64KB of memory.

 

[KC9UDX]

This seems to be a frequent discussion at 6502.org. in fact, it was brought up very recently again.