6809 instead of the 6502

[EvilSnack]

Aside from having to rewrite the entire ROM, and perhaps having to add an adapter to accommodate any pin-out/power requirement variation between the two CPUs, what's stopping an ambitious experimenter from replacing the 6502 with a 6809?

 

[Scott Robison]

I think you've nailed the reasons right there.

[Wavicle]

I was going to say because they don't make them anymore, but apparently that isn't true. That said, new stock is expensive and limited to 2MHz.

[Scott Robison]

On 10/27/2021 at 6:06 PM, Wavicle said:

I was going to say because they don't make them anymore, but apparently that isn't true. That said, new stock is expensive and limited to 2MHz.

True, though X16 isn't letting the whole "no new stock" thing stand in the way of sound chips, so hacking an old 6809 or similar chip is doable from that perspective.

[codewar65]

The 6809 was a wonderful CPU. As much as the 6502 is. I know more 6502 and the 6809, but the 6809 was: New Old Stock.

 

[paulscottrobson]

It was always such a shame that the 6809 got paired so much with the 6847 which makes games look like the colour was vomited onto the screen (I presume there was some technical reason for those colours because no sane person would choose them voluntarilY).

An 8Mhz 6809 (in FPGA) and Vera would be an awesome machine.

Also it's enjoyable writing for that sort of CPU. Writing 6502 assembler you always feel you are fighting it.

[BruceMcF]

On 10/27/2021 at 3:03 PM, EvilSnack said:

Aside from having to rewrite the entire ROM, and perhaps having to add an adapter to accommodate any pin-out/power requirement variation between the two CPUs, what's stopping an ambitious experimenter from replacing the 6502 with a 6809?

Though it wouldn't be necessary to replace the 6502 it it's on a bus mastering expansion card.

[Ju+Te]

What actually speaks for a 6502 (or sibling) except of the nostalgia factor and to reuse some parts of existing C64 software? Aren't there better 8 bit processors? Because of the different hardware, especially VERA, software needs to be adopted anyway.

[Scott Robison]

"Better" depends on what you are trying to measure it against, and is subjective because it depends on what the individual values most. So by some measures, yes there were better 8 bit processors.



But no, there aren't better 8 bit processors. ?

[Ju+Te]

With better I mean for example:

1) does it need additional chips for timers, ports?

2) are other processors with more registers faster/slower for the same tasks?

3) what is the available max. clock count (related to 2)?

Independent of that - how large is the effort to adopt software to run on the X16, especially compared with other 8-bit processors? IIRC, the 6502 was not part of the "dream 8-bit computer definition".