BIOS automatically goes to CD player after ~10 seconds

[adimifus]

Using either a US or EU Mega CD model 1 BIOS (region patched or untouched), the looping animated BIOS screen will automatically go to the CD player after approximately 10 seconds. If a game is loaded, it will automatically start in around the same amount of time. Neither of these things happen with JP model 1 BIOS or any model 2 BIOS.

This bug has been confirmed by at least 2 other users: https://misterfpga.org/viewtopic.php?p=89532

Real hardware will sit animated BIOS screen indefinitely and will not switch to the CD player unless a button is pressed.

The MegaCD core didn't used to do this (it used to act like real hardware), but I can't say for sure when this issue started.

[birdybro]

What bios are you using specifically? I'll test this out too...

Testing with Sega CD (U) - Model 1 v1.10 (1992).bin (MD5: 2EFD74E3232FF260E371B99F84024F7F) - Does the same thing until 20230224, but before where this bios doesn't even work, so it's an improvement nowadays over previous.

That's the only United States region coded BIOS for the Model 1 that I see here with a version 1.x.

[adimifus]

The BIOS file I've tried are here: https://segaretro.org/Sega_Mega-CD/Boot_ROM

I've also tried l_oliveira region patched BIOS files, but I don't recall where I got them.

[birdybro]

Yeah same result with USA version 1.00.

How do you know this used to be working? It apparently wasn't working at all with v 1.0 bios files before 20230224

[adimifus]

Yeah same result with USA version 1.00.

How do you know this used to be working? It apparently wasn't working at all with v 1.0 bios files before 20230224

I've been using the MegaCD core since it was first available, and I used to be able to just load it up and have it sit there at the animated boot screen. At least one or two times I was running it alongside my real Sega CD model 1 to compare them, and to adjust my video settings. I don't recall if I ever tried v1.0, but I know one of the US model 1 BIOS files worked for sure since I would sometimes just load it up and let it sit there cycling away it's animations.

[birdybro]

Please download this repository and copy the contents of the releases folder to a new folder on your MiSTer named _Test. Tell me which release works properly with your model 1 bios in your testing.

[adimifus]

Ok here are my results:

The latest combination of MiSTer binary + MegaCD RBF that doesnt interrupt the boot animation is: MiSTer_20230526.bin + MegaCD_20230224.rbf

With MiSTer_20230703.bin, the animation is interrupted on MegaCD_20230224.rbf like it does now.

Starting with MiSTer_20230716.bin, MegaCD_20230224.rbf no longer boots properly (sits at boot animation screen with only static background and doesn't respond to input)

I tested with US v1.00, US v1.10, US V1.10 region patched, EU v1.00 and EU v1.00 region patched.

EDIT: I should also mention that MegaCD_20230716.rbf and newer don't work with MiSTer_20230526.bin. It will only boot to a static background image with no animation and no response to input.

EDIT 2: Additionally, with MiSTer_20230526.bin all revisions of MegaCD earlier than 20230224 also work properly.

[birdybro]

Thank you, that is going to be more helpful. It seems like the issue is in the Main MiSTer binary, rather than in the core maybe.

Maybe something with this commit would be relevant?

https://github.com/MiSTer-devel/Main_MiSTer/commit/71a8caacde94dd4ba31eea4a91b776f7f5a0a25a

Not saying this is the cause, it might be incidental.