Sega CD - Chuck Rock game freezes in intro

[KamiLordus]

The game freezes at the beginning of the intro. You can hear the narrator and sounds, but the animation is stopped.

Windows 11
Retroarch 1.18
Genesis Plus Gx core latest
Chuck Rock (USA) - chd file format

Retroarch log file:
retroarch.log

[ekeeke]

I can confirm this is a regression introduced by commit 47761b9

Most probably, this was working by chance in earlier versions but above commit slightly modified main-cpu execution timings just enough to break synchronization between main-cpu and sub-cpu. I will need to analyze this further.

Note: I also noticed that since this other commit (dd61951), that game (and maybe others from Sony Imagesoft which share same boot routines) was taking much longer time at the Sega logo so this is another thing to lookup.

[KamiLordus]

Wolfchild seems to have a very similar issue. The game freezes on the Sega logo, but if you wait a bit, or use the fast forward option in Retroarch, you can hear the music playing.

[jmaneyrol69]

It has actually become worse, even with the latest commit from libretro@7b57513 : now all Core Design segaCD games I have tested so far have become unusable.

They all boot-loop right after the "Sega" boot logo. I have reproduced on Linux and Android with:

• Wolfchild (USA)
• Chuck Rock (USA)
• Wonderdog (USA)

My images are in CHD format.

Also, they work with other emus, such as PicoDrive.

[Freakservo]

Confirming Core bug -- Chuck 2 and BC Racers also freeze, and Thunderstrike sometimes freezes after the opening cinematic (Other times at SEGA logo; About 50/50.)

[jmaneyrol69]

Some precision too ; the problem seems to differ depending on the system.

On Linux & Android, those games just loop boot right after the Sega loading logo (the one where we see Sonic).

On Windows, it goes further but then freezes, usually after the intro (Chuck Rock) or some time after the loading screen (WolfChild). Anyway, in all cases, Core games are unplayable on Sega CD for the moment with this core.

[ekeeke]

From experience, it differs depending on BIOS version used so most likely you have different BIOS configured on these different system.

Anyway, my spare time for working on this emulator is close to 0 these days and so far, there has been nobody else but me investigating emulation bugs so, unfortunately, it's not going to be solved soon. I looked briefly to it some times ago but it's kinda hard to figure out the root cause as this is likely a synchronization issue between the two CPUs, which is quite hard to debug.

For the time being, the only solution is to revert to an older version (previous to the commit indicated above).

[jmaneyrol69]

@ekeeke thank you for the details. I'm pretty sure I use the same BIOSes on all my systems. However, I have not tested other versions than US so far, I'll see what happens with EU/JP.

I hope you'll have enough time & support in the future to look further into the issue, and no worries, there are other options to run those games (though it will be nice when it is fixed ;-) ). Take care!

[Freakservo]

tOkay then -- Workaround time! =)

After taking a bit to mess with the options, I discovered turning 'CD Access Time' off in the 'Emulation Hacks' menu gets these games moving. I only ran them as far as their title-screens, but all Core-developed games seem to function with this one option deactivated.

Mind, this is only tested on Windows and with US Bios 1.10 and 2.00. Your mileage may vary on other formats.

[EDIT] Guess I goofed a bit! Turning off 'CD Access Time' does seem to move the games past the 'SEGA' logo, but Chuck Rock will now freeze on the first scene of the intro (Cannot be skipped). Similar issue with Wolfchild, but further into the intro (Can be skipped). The rest seem to be working.