6809 instead of the 6502

[Scott Robison]

On 10/29/2021 at 9:34 AM, Ju+Te said:

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".

There are microcontrollers built around a 6502 style core, so sometimes you don't need extra chips.

Faster and slower varies based on usage. 6502 had a slower clock usually than 8088, but the 6502 was more efficient at memory access so clock speed didn't matter in those types of cases. But with more registers it might not be as big of a deal. So faster clock isn't always better.

6502 was definitely part of David's "manifesto" as he wanted an 8bit computer like unto the C64 or VIC-20. And we can have much faster 6502 style computers today than were practical back then.

[Wavicle]

On 10/29/2021 at 8:34 AM, Ju+Te said:

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".

I found out about the project after the first "Building my dream computer" video, so I am not certain about things prior to that, but in that video 6502 was definitely part of the plan. The original plan was to use a C64 with the video, keyboard, and storage hanging off expansion ports. This would give a stable platform for developing the kernal and once done the C64 PCB should be replaceable by any commodity (or bespoke) 6502 PCB.

I've worked on teams building hardware or silicon ASIC products for the last 15 years and thought this original plan was well grounded: it kept things simple; started from a known working point; and provided a fast path for the software team to start developing on real hardware. Somewhere along the way, feature creep came to visit and promptly made starting with a C64 impossible. My experience told me that this was going to result in higher cost, longer dev time, or both -- but that experience is limited to commercial efforts at companies with deep pockets so maybe it wasn't tuned for this environment... or maybe it was. Switching to an MC6800 variant would be committing to this all over again unless there is a readily available source of commodity MC6800 boards.

[Ju+Te]

The emphasis laid on "it would have a real CPU" (probably in contrast to some emulation or FPGA) and the 6502 only was mentioned in the accessory sentence. So it seems, both views are valid.

[Scott Robison]

On 10/30/2021 at 2:16 AM, Ju+Te said:

The emphasis laid on "it would have a real CPU" (probably in contrast to some emulation or FPGA) and the 6502 only was mentioned in the accessory sentence. So it seems, both views are valid.

True. There was some evolution of the ideas over time, from his initial blog post to that video and subsequent videos.

[EvilSnack]

I understand the reasons why few would attempt this. The 6809 seems to have been a victim of bad timing. I've coded for both the 6502 (including a word processor for my C64) and the 6809 (several attempted games for Dad's CoCo), and the latter simply had that much more potential.

[Scott Robison]

On 11/26/2021 at 2:18 PM, EvilSnack said:

I understand the reasons why few would attempt this. The 6809 seems to have been a victim of bad timing. I've coded for both the 6502 (including a word processor for my C64) and the 6809 (several attempted games for Dad's CoCo), and the latter simply had that much more potential.

As many companies have proven over time, you don't have to have the best product to gain the most traction and take control of the marketplace.

[Edmond D]

On 11/26/2021 at 3:15 PM, Scott Robison said:

As many companies have proven over time, you don't have to have the best product to gain the most traction and take control of the marketplace.

Yes - I think pricing may be a factor, according to the wikipedia article - https://en.wikipedia.org/wiki/Motorola_6809



I had the pleasure of using a SuperPet in  the 80's and all the Waterloo languages - they had dual CPUs of a 6502 and the 6809.

[Scott Robison]

On 11/26/2021 at 8:05 PM, Edmond D said:

Yes - I think pricing may be a factor, according to the wikipedia article - https://en.wikipedia.org/wiki/Motorola_6809



I had the pleasure of using a SuperPet in  the 80's and all the Waterloo languages - they had dual CPUs of a 6502 and the 6809.

I've heard a lot of good about 6809. My wife's uncle swears it is the best CPU ever. ?

[kelli217]

On 11/26/2021 at 10:24 PM, Scott Robison said:

I've heard a lot of good about 6809. My wife's uncle swears it is the best CPU ever. ?

It's certainly in the running for the best 8-bit CPU ever. I don't think an OS like OS-9 could have been written on anything else.

[Edmond D]

Alas, as a teenager at the time CPU type was a small thing compared to the amount & quality of accessible software (read games?) the platform had. The only 6809 specific software I had access  to was the Waterloo languages. They were great for learning and set me up for the many other languages that followed. 

I'm not sure if the X16 had a 6809 I'd be so eager to buy one (or others) given the amount & volume of 6502 based computer systems (and games) from the 80's. That's not to say the 6809 systems were bad; the  just weren't what I used.



Going back to the originating post, once the X16 ships then perhaps someone will experiment with such as system. Perhaps  when/if a stand alone VERA board is released, a 6809 system is designed to use it.