Why C= never made a 65816 based machine?

[cgutjahr]

You're missing the point... yes, it wouldn't be the fastest machine around, but that's not what it's for. It would be dirt cheap and plenty fast. A early 90's C64...

You are missing the point. This is not just about speed - it's about price, target audience and percieved value for money.

The C64 was still selling like crazy in 1990, while the A500 had dropped below the 1000 DM/350 UKP mark by then. Between these two, there was simply no space for another machine. The C128 had been discontinued for that very reason, despite selling better than the A500.

Introducing another machine between these two would have just hurt sales of the existing two options. It would have made an A500 look to expensive or the C64 to slow. Not to mention that a third incompatible platform would have been extremely stupid, especially as late as 1990.

As somebody already said: the C64, the A500 and (to a lesser extent) the C128 were handled properly. The real problems were the lack of focus, the lack of advertising and the number of crappy computers (+4/C16/C116, A500+, A600) Commodore released, apparently to stop their best sellers from becoming too successful.

[cgutjahr]

It's not compatible enough. Both for timing and the instruction set.

I used to have a SuperCPU, and it was pretty compatible, AFAIR. The official 6502 instruction set was fully supported, it just didn't handle illegal opcodes. But that was more of a problem when watching demos, most games and especially applications worked fine.

[cgutjahr]

The 65816 was (briefly) considered for the C128 design, but a lot of people in engineering weren't exactly fans of the CPU design and software support (read: assemblers) was very immature in 1984.

Before the A2000 and A500 were greenlit, Commodore Engineering was proposing a range of different projects. One of them was a C128 follow up referred to as "BMW" and "C256", IIRC. Hayne was designing the specs, and he wanted to include a 65816, despite concerns from other engineers. That machine would not have been compatible with the 64, it would not have had CP/M and I imagine it would have been barely compatible with the 128. It got killed when new Amiga machines became the only priority.