How I Solved the DC VA0 JAP Black Screen Issue in Four Games!

[CrisMod]

Hello, folks! As I was going through my Dreamcast library to compile a comprehensive list of working settings/presets for running games with the Dreamshell IDE modification in 2023, I aimed to provide an easier way for the community to access and enjoy these games, especially with the specific hardware combination I'm using (which I'll share once the list is complete).

I've encountered a peculiar glitch issue in certain games that only affects the Japanese Dreamcast VA0 model, and I haven't been able to find a solution for it, even after seeking advice from various sources. Let me clarify that I'm well-positioned to make this assertion because I own three different Dreamcast models from various regions, and I'm a self-taught modder who ensures my Dreamcast consoles are in top working condition from a hardware standpoint.

While conducting experiments on my Japanese VA0 Dreamcast, the first game affected by this problem was "Looney Tunes Space Race." This game refused to boot on the VA0 Japanese Dreamcast, as it worked fine on the VA1 Japanese version. The farthest I could get with various Dreamshell settings was the Sega logo, followed by a black screen.

I tried everything with DreamShell, different types of dumps, and every possible combination of settings, but the game wouldn't start, and I was certain that it wasn't due to the modification. Following this, I conducted experiments with the three different Dreamcast models, using the real GD-ROM and physical discs. To ensure a precise, scientific verification, I performed a third test with the serial port and the same adapter and SD card in all three consoles under identical conditions (same gamepad, same VMU, renewed PSUs, all three with renewed GD-ROM hardware, and I even tried it without the VMU), and the "VA0 Japanese" model consistently experienced the black screen issue when running Looney Tunes. Other games worked fine up to that point, leading me to believe that there's something unique in the VA0 Japanese hardware that hasn't been noticed before when compared to other Dreamcast versions (even in front of the VA1 Japanese version, which booted the game without issues).

Setting aside Looney Tunes, as I continued with numerous tests, I encountered three more games with the same problem, bringing the total to four games (out of an extensive library of nearly 650 games). This issue seemed unrelated to the game's region or version. The affected games are:

1. Looney Tunes Space Race.
2. Soldier of Fortune.
3. Speed Devils - Online Racing (only the online version; the normal version doesn't have this glitch on the VA0 Japanese model).
4. UnderCover AD2025 Kei (Japan).


Thanks to the last game, UnderCover AD2025 Kei, I discovered the glitch that resolved the boot issue for the other games. In UnderCover AD2025 Kei, the game consistently froze at the same point after nearly 15 minutes of gameplay. Initially, I thought it might be a loader or incorrect settings causing the block, but the strange part was that the game always froze at the same point with other settings as well. So, I considered it might be an issue with the image and tried different ones, but the problem persisted. As a last-ditch effort, I tried playing without the VMU, and the game still froze.

Frustrated after countless hours of tests and unsuccessful attempts with Dreamshell, I began to suspect that the issue might be related to the VMU's memory access. My VMU had been filled with save data after testing over 600 games, and I thought that maybe using a different empty 4MB VMU or what so ever in place of the original one could provide some form of memory control at that specific point (I had tried playing without the VMU earlier, and the problem still occurred). To my surprise, using the empty VMU allowed the game to proceed without freezing. Remembering the other three games, I speculated that perhaps these games were being blocked by my original VMU because it had created a kind of barrier to memory access.

Inexplicably, to my amazement and relief, all four games became unblocked and started without any issues!

From what I understand, this glitch if happen it seems to “nests” somewhere in the Dreamcast's memory, data bus or RAM (?!). Resetting the Dreamcast doesn't resolve the issue, and it's not directly tied to the VMU because, without the VMU, the games would still freeze. Instead, it requires a different electrical stimulus related to data transfer on the bus to unlock the error or glitch that occurs initially with these listed titles. If this glitch occurs, it may also affect other titles that rely on VMU control during boot if the VMU's memory is filled with save data. I'm not sure if a different VMU is needed to resolve this glitch, but using a different freshly formatted VMU takeout the glitch and certainly does the trick. Even if you switch back to the original VMU that caused problems before, the glitch doesn't reappear because there seems to have been a "reset" of the error. However, it's advisable to run these listed games with a VMU that has free memory space to avoid encountering this problem on the VA0 Japanese model.

I hope this guide and information help others who, like me, have scratched their heads and nearly gone mad trying to find a solution.

[Ingick]

Thanks for the info