6809 instead of the 6502

[TomXP411]

CP/M still requires a BIOS that has the drivers for that system's hardware: at the very least, disk drives and console drivers were necessary and usually different for different systems. However,  writing a BIOS is a lot simpler than an entire operating system, which is what the Commander team was faced with. Fortunately, licensing the Commodore ROMs short-circuited a big chunk of that. 

Also, there's the obvious fact that a ROM based OS can't be significantly updated without problems. Looking at the differences in the last few CX16 emulator versions, for example, clearly highlight that. To make 320x240 graphics possible, Michael had to relocate the text buffer. And that broke a ton of stuff. With a disk based OS, you can solve this problem by simply booting to a different disk for stuff that needs the older configuration.

 

 

[Edmond D]

On 6/6/2022 at 7:12 AM, mobluse said:

ntel 8088 is also an 8-bit CPU since it has an 8-bit data bus.

It actual was a 16 bit CPU limited with an external 8 bit bus. See https://en.wikipedia.org/wiki/Intel_8088



But more on the 6809 which was a 8 bit cpu with some 16 bit features - https://en.wikipedia.org/wiki/Motorola_6809 



While many liked the CPU in the few 8 bit machines that it was used in, I don't think it would have the same market appeal as a retro machine based on the 6502 processor. 



The thread started with considering making a CX16 use a 6809 processor as a drop in replacement. The technical issues I feel limit that possibility.

However, I could see a 6809 retro-computer being built by taking the CX16 design and adapting it to the 6809. Video (VERA) might have the power to emulate what the CoCo could do. I think fans of that system would be happy to have a redo clone.



Note that I was a commodore teen and didn't spend much time on the 6809 save for the  high school's SuperPet I was assigned to (one of the benefits of upstage a typing teacher forced to try and teach computers/BASIC which was really out of her depth.)

[rje]

So what sort of operating system did the SuperPET's 6809 use?  Did it have a modified KERNAL?

 

[kelli217]

It had a startup menu from which you could load any of a number of microcomputer versions of then-popular languages, such as BASIC, APL, FORTRAN, Pascal, or COBOL. They were developed in conjunction with the University of Waterloo in Ontario, Canada.

[Edmond D]

On 6/10/2022 at 7:34 AM, rje said:

So what sort of operating system did the SuperPET's 6809 use?  Did it have a modified KERNAL?



 

There was a switch on the side which allowed one to choose the processor that the machine would use. I'm unsure of the kernel/ROM modifications from the original PET. It did have a dongle built-in which I didn't know about when I sat in front of it. The copy protection seems a little excessive, as the whole machine was effectively a dongle. Perhaps it was designed/included because the machine targeted university computer science students with the assumption that they are smart but criminal. ?

There is a light article here https://www.oldcomputr.com/commodore-mmf-9000-superpet-1981/ which is a good initial overview. The manuals for the system & languages have been reproduced online and can easily be found. 

 

[BruceMcF]

On 6/11/2022 at 9:57 AM, Edmond D said:

.... Perhaps it was designed/included because the machine targeted university computer science students with the assumption that they are smart but criminal. ? ...

Some would express the "assumption" part as, "... with the awareness that they are..."

[Johan Kårlin]

On 10/29/2021 at 10:20 PM, Wavicle said:

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 haven’t rewatched the videos, but as I remember it the plan was to use 65816, a 16 bit successor to 6502. The reason was that while 6502 might be more nostalgic the experience of programming it is rather tedious. Everything tends to be about handling low and high bytes .. But the 65816 were abandoned because of difficulties with the hardware implementation. If you search for ”65816” in the facebook group you can find discussions about this from around three years ago.

[Johan Kårlin]

On 10/29/2021 at 10:20 PM, Wavicle said:

 

[Johan Kårlin]

-

[svenvandevelde]

On 6/12/2022 at 2:51 PM, Johan Kårlin said:

I haven’t rewatched the videos, but as I remember it the plan was to use 65816, a 16 bit successor to 6502. The reason was that while 6502 might be more nostalgic the experience of programming it is rather tedious. Everything tends to be about handling low and high bytes .. But the 65816 were abandoned because of difficulties with the hardware implementation. If you search for ”65816” in the facebook group you can find discussions about this from around three years ago.

Really? Well to be honest I am kind of glad that the 65C02 was selected, although it would have been nice if the 65CE02 would have been possible. The additional z register would really make a difference. It would allow for less zero page usage etc. But the 65C02 really gives that commodore feeling!