[BUG] Metal Stoker - Game Hangs and/or graphics get corrupted during gameplay when taking damage

[VinniePC]

Hello again 😁

I've tried playing Metal Stoker on Geargrafx and I have the following issue:

After skipping the intro and starting the game by repeatedly hitting RUN, try to immediately take at least one hit from any enemy, after a short while the game will hang and the graphics may or may not get corrupted as well.

I am quite sure that the prerequisite is to take at least one hit from the enemy as, without taking any damage, I was able to progress further above. Some screenshots of the game when it hangs. Usually it will also change the resolution when hanging. The first screenshot is from when I was able to progress a bit without taking damage.

This can happen almost immediately, within 10 seconds from taking a hit or much longer when I got further through the level before taking any damage (There I actually lost 2 lives before the game hanged) but I consistently either have the game completely hang with or without the graphics being corrupted, a few times the music continued playing while the screen was corrupted.

Would it be possible for you to look into this game? 🙂

[drhelius]

Thanks for reporting.
I'm swamped with work right now but I will take a look as soon as I can.

[Ryusennin]

Interestingly, it's not just corrupted visually; the collisions seem to break along with the map. I got stuck by some broken tiles after clearing the second screen and trying to move to the next one.

[drhelius]

It's quite normal that when the game is not executing the right code at the right moment it ends up modifying not expected registers in the hardware that causes changes in many other systems and configuration like changing res or corrupting other memory areas.

For your descriptions here I'm suspecting a bad IRQ timing. PC Engine is extremely difficult regarding timing.

[drhelius]

Just debugged it a bit and this game is very sensitive to vram wait states and deferred I/O. It is definitely missing or acknowledging IRQs with bad timing.

This two things are quite hard to emulate and it is something in my TODO list, but won't happen soon.