How hard to simultaneously develop a game for 5200 / A8?

[CannibalCat]

Hey all, I know I may have seen some talk of this in the past, about developing a game for 5200 and Atari 8-Bit computers simultaneously... are there any resources out there and/or tips on time saving approaches? Should one platform be completed before re-working it for the other?

[+JAC!]

I just recently did a port of an Atari 8-bit game to a 5200. In fact you can do it with a single source in parallel if you stick to some rules.

I have two "Main" Files that define the system specifics and a single "game" include.

 

http://atariage.com/forums/topic/224914-alien-swarm-hack-request/?p=3078433

Edited October 14, 2014 by JAC!

[CannibalCat]

Excellent, thanks so much. Would be awesome if you did ever get around to doing a tutorial video on the subject... love your other videos as well!

[+Stephen]

Seconded - more videos please. The gf even watches them with me

[Rybags]

Developing for both in parallel would make things harder in that you have to apply constraints that the 5200 imposes to both versions.

Main one being that only 16K Ram is available.

Other issues are pretty trivial mainly:

- Controller input very different but seperate routines translating input to a common format would be easy.

- IO addresses different except Antic, simply using labels and conditional assembly can take care of that.

- OS services different, fairly easy to cater for, ie do it within the program and take that dependancy away.

- Ram-based OS variables different. Once again, do your own shadowing and services as above.

- cartridge address space 32K for 5200 only 16K possible on computer. Banking schemes can be various on both, a banked 16K cart scheme could be used on both where top 8K is static and lower 8K changes, actual switching mechanism would likely be different but once again seperate routines/conditional assembly makes it easier.

[MaPa]

Different HW address space can be easier to manage with XASM assembler. This is extracted from the XASM help:

 

Abbreviations of Atari hardware registers are provided to save two characters ($d40e vs ^4e) and to facilitate porting software between Atari 8-bit computers and the Atari 5200 console. These are very similar machines, one of the biggest differences is the location of hardware registers.

[Wrathchild]

I'll pick one of the conversions I've done and post up the sources for it.
These are generally split into two folders, one for each platform, and so a diff-tool can easily highlight the typically changes required.

 

Having done A8->5200 ports, these tend to supply a replacement joystick/keyboard engine in the 5200 to simulate the digital joysticks on the A8 but aside from that it is mostly memory layout considerations ($4000->$BFFF = ROM on 5200)

[CannibalCat]

Thanks guys, these are all great considerations.

[ClausB]

http://atariage.com/forums/topic/130940-article-transporting-atari-computer-programs-to-the-5200/?do=findComment&comment=1580189