Does not work on Ultimate 64 Elite I with firmware 3.15

[chrisgleissner]

Amazing work! Really love what you did here.

I tried to get it to work on the new firmware 3.15 for the Ultimate family of devices. In my case, I am using the Ultimate 64 Elite I.

However, using version 1.0.0 of your game, immediately after the intro logo, I just get the following garbled screen and the game stalls:

Would you mind trying it out on the new firmware 3.15? You can find it on any test-merge branch of Gideon's repo. The latest buil artifacts are at https://github.com/GideonZ/1541ultimate/actions/runs/32724357347

Thanks

[chrisgleissner]

Additional context: There appears to be a regression in the 3.15 firmware which your game highlights. So thanks a lot for having created this game as it proves very useful to fix these regressions.

Defect Types

Two different defects:

• Flickering of some game areas, but game otherwise renders OK. This flickering seems to have a frequency of around 10 to 15 hertz and it looks as though parts of the image get temporarily replaced with a brighter version. The flickering is very regular, but only affects parts of the overall image.
• Complete engine degradation, as shown in the picture earlier.

In case you happened to come across these two defects during game development, it would be interesting to learn about it, as it could shed more light on the underlying defect.

Bisection Harness

Please note that I created a bisection harness for your game. Have a look at GideonZ/1541ultimate#804

The interesting part is that as I progress through changes that were made for the 3.15 firmware, there are sporadic regressions resulting in a flickering image, only for these flickers to be rectified by a later release. It would be interesting for you to run this yourself and look at some generated Mp4 videos which illustrate the issues. If you are interested, I could also share my results with you.

Questions

In bisecting this issue, I have come across many instances for sporadic flickering of the gameplay area. The frequency of the flicker varies.

Some questions:

• Did you ever encounter this during development of the game, and are there cases of flicker even on the 1.1.0 C64U firmware?
• Do you have any assertions in the code I could use as part of the bisection to determine whether the rendering is entirely correct?