Running Harmony Arm code Native on Raspberry Pi?

[barnieg]

I'm not sure whether is possible or practical but thought I would ask to see if any of the following is possible:

 

How is the Harmony emulation (is that the right term?) dealt with on an Arm processor does it run natively and if not would this be possible?

 

Would would be the feasibility in adapting Stella + Batari Basic into an retro type interpreter?

 

Is it worth using Batari Basic as the base for a bare metal coding platform for the Pi?

 

 

Any thoughts input on this?

 

 

Barnie

[+batari]

It won't run natively for a number of reasons.

 

First and foremost, the R.Pi is not binary compatible with the ARM7 chip used in harmony (different instruction set.) even if you had source, you could not port it as it's largely ARM7 assembly language and in order to make it work, the predication and barrel shifter features were used extensively (nice features which were crippled in later ARM cores) and many special registers were used creatively (I.e. not for their intended purposes) and later cores lack these registers completely.

 

No, this doesn't mean the bios is a hack but instead a creative way of programming much like 2600 programmers do every day.

 

Another consideration is the mapping of memory and memory-mapped ports may not be compatible. They are hard-coded for speed and efficiency on harmony because they have to be. While the R.Pi might have a MMU that could help some of this along, it might not be flexible enough. Likely GPIO will be a bigger issue.

 

Basically one would need to start from scratch. Considering it took a year and a half to finish the first usable bios, it probably wouldn't be worth it. And by then it wouldn't be a harmony or even a clone but its own independent device.

[barnieg]

I didn't know Arm had broken backwards compatibility to that extent! It seems to be the other extreme of PC Architecture where current Desktops are still lumbered with remnants of the past.

 

Maybe another answer is to have harmony integrated with a new fpga atari clone? Something that is reasonably cheap and builds on work that has already been done