Articles by Retro Ports

Since it has been over 2 weeks since the last update, I thought I’d better post something.

Whilst I have been focusing on life off the computer lately (namely an 82km fun/charity bicycle ride) I have managed to make some progress. What I haven’t made any progress on, however, is the …

No progress on the collision-detection bug so I decided to implement the double-buffering (page flipping) since it is almost trivial and won’t be affected by any other programming issue.

The arcade machine uses a pair of so-called “ping-pong” buffers to allow the DVG to render the frame whilst the CPU is …

Today I had the chance to review the collision-detection code. The bad news is that I couldn’t see anything amiss. I did find a few minor issues to do with ADC/ADD but they don’t appear to be the cause of the bug. I also managed to effect a few minor …

More tweaks to the display mapping, and it’s improved even more. There was an offset added in the core (arcade) code when adding the CUR command to the DVG display list that must be peculiar to the vector hardware; I needed to remove that offset to enable objects to use …

Another brief update; I seem to only get to work on it in snippets atm…

I’ve fixed the ship explosion offset (same as ship offset). I also fixed a long-standing bug in the erase routine for the extra life indicators.

It’s looking pretty spot-on now as far as object placement goes, although …

Super-brief update… I’ve fixed the ship/shot offset issue. Nothing sinister at all – simply forgot the ‘#’ character when adding the fixed pixel offsets to the accumulator!

Need to re-check the other offsets now, and fix the display issue at the bottom of the screen, and possibly add Y clipping – …

Very brief update.

After five days away from the keyboard I decided there was only one possible reason for the erase ship routine not working… and I was right! Because I cut-and-paste the render routine and used it for the erase by replacing the video writes with CLR, it simply wasn’t …

After adding the thrust (pixel) rendering, I decided to bite the bullet and implement the ship explosion to round off the port before I move on to optimisations for the Coco3.

I’ve ported all the original code, despite the fact that one of the routines isn’t required for the Coco3 (or …

I’ve finished the RE of the exploding ship routines, both in the original and Norbert’s emulator.

Norbert patches the explosion routine to call his routine to render a piece – using intermediate results from the caller – and then jumps back to the original routine. There’s a decent amount of code …