sega cd - BC Racers Strange behavior and black screen in android

[BlitBit]

I have seen all this in:
Android: 16.
Retroarch : 1.22.2.
Genesis-Plus-GX: 1.7.4 c858c9c.

In the scene cuts, the geometry of the image appears to be deformed by a frame. (This effect is noticeable as soon as the SEGA logo disappears with Sonic next to it) After this in the start menus the spearheads that indicate the selection flash irregularly and respond to the controls inputs also irregularly. After this, when you start the game, only a black screen remains.

none of these behaviors are seen in the Genesis-Plus-GX-Wide core or another kernel for Sega CD emulation.

PS- although on the Genesis-Plus-GX-Wide core the Load times between scene cuts seem somewhat long.

[ekeeke]

This is now fixed upstream by ekeeke@9602192

For the record, this was caused by synchronization issue between Main-CPU and Sub-CPU, introduced when 68k bus refresh delay emulation was added: Sub-CPU is accessing communication registers, which triggers Main-CPU resynchronization (by running a few instructions to catch up Sub-CPU cycle count) but, depending on timings, Main-CPU could potentially write communication registers itself during this timeframe and trigger Sub-CPU resynchronization, which would cause Sub-CPU to execute next instruction although the former one was not fully processed (as memory access occurs in the middle of instruction processing) and, as a result, lead to unexpected behavior. Above commit prevents such potential recursive execution.

[KamiLordus]

Hi @ekeeke, is there any reason you no longer support the Genesis Plus GX core for Retroarch? I mean, the upstream patches are being ported to the RA platform by someone else.

[ekeeke]

Not sure what you mean by "not supporting" but synchronization with upstream has always been handled by libretro team, not me. I don't have any access rights to this repository and have enough on my plate with my own repository, synchronization with core changes I do upstream into the various Genesis Plus GX forks is the responsability of the forks maintainers, not me. I only look here from time to time as retroarch users often tend to submit core emulation issues here instead of upstream repository but i don't have any control on this repository

[KamiLordus]

Well, then I apologize for the confusion :)
I was sure you were the one who made the changes to the RA core some time ago.