Shots fired and number of hits rollover

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Shots fired and number of hits rollover

Post by Barra » Wed Jan 02, 2019 6:40 am

I did some testing today regarding where the rollovers occurred for both the "shots fired" and "number of hits" values that appear after your game ends.
Originally I had always assumed the rollover point was 100k, but had never done the math or looked into it any further.

Mike Thompson brought the topic up and said they both rolled at approximately '65555', so I decided to test it out to see exactly where.

Shots fired:
Shots fired rollover.png
Shots fired rollover.png (6.05 KiB) Viewed 389 times

Number of hits:
Number of hits rollover.png
Number of hits rollover.png (6.28 KiB) Viewed 375 times
As you can see they both rollover at "65536", which happens to be a 16-bit integer. I was wrong all these years about my 100,000 assumption!

There's probably a better way of testing but all I did was load up Galaga in MAME with cheats enabled (specifically fast shot, invincibility and auto-fire) and pressed F10 to disable throttling
It got a bit tedious homing in to the exact value, requiring multiple save states and re-loading

Good stuff Mike and nice catch! :)