conversion question

[Poison]

hi, is possible or easy make conversion of the games from atari systems 2600 or 7800 ? Many games are from a2600 on a8. But nice games such as Double dragon or kung-fu master not. Is possible to convert one? Is it harder than from BBC or zx?

[Heaven/TQA]

the architecture of 2600 & 800 esp. the sprite hardware is different... same of 7800 which is far more different...

[Rybags]

2600 would be a lot easier - you can replicate many things fairly straight-forward except probably the playfield but a conversion routine wouldn't be too much effort.

But, don't some games have Player reuse on the one scanline - stuff like that would make it harder.

 

7800 in many ways is a more powerful system and somewhat different, so much more work there.

[Heaven/TQA]

Rybags... well...the HPOS and REPx is different behaviour...so I am not sure how you would translate that into the 800 architecture... I don't mean to get the engine and write a new gfx engine but to take nearly 99% of the code plus some patches are not enough I think...

[Rybags]

I think a better alternative anyway, with all the cross-platform tools and disassemblers, would be to just reverse-engineer into source code, then strip the kernal and just use traditional rendering techniques.

[Wrathchild]

My comment would be to pick the title you'd like to convert carefully, i.e weigh up what advantages the title is making of the original h/w.

 

I did begin porting 'Combat' and initially keeping it in the 'kernel' model of programming was going OK. There was some re-work required in doing the background (as Rybags suggested) due to the 2600 being able to 'mirror' playfields. I think timing of what needed to be done within one vertical line put paid to the kernel mode as it resulted in the tank not being shown on the correctly or 'hopping' between lines and also missiles not drawing all of the time.

 

I have code where I've begun making a more A8 friendly version where work is pre-prepared and registers updated in the VBI instead, but there are still a few things there too be ironed out.

 

Finally, the current version only does tanks. The 2600 has a trick by which it can double or treble (I think) display the sprite on the horizontal and so this is how you get the plane game variations. We have the spare players/missles to handle this on the A8 but there is an overhead in code to manage this, wheras its for free on the 2600.

 

Also I think I found the sound chip on the 2600 also doesn't have a direct equivalent to map this to the pokey, and so extra work is required there.

 

Srdečné pozdravy,

Mark