The Jaleco Megaystem 1 driver is broken to an almost shambolic level, nothing really works as it should. This is mainly down to interrupt handling, timing, sometimes subtle protections, and generally things not being understood well. It did used to run ‘better’ but even back then it was held together with hacks.
If you’re expecting this post to be about Ninja Kazan (Iga Ninjyutsuden) being fixed, or the random sprite lag being fixed, or Takeda Shingen / Shingen Samurai-Fighter crashes being fixed then stop reading now, they’re not, I have no clue how to fix them without resorting to the hacks of old, and I’d really rather not do that.
Kale did add a video RAM mirror allowing the background destruction to function correctly in 64th Street (characters still don’t move during attract tho) and so I decided that while fixing the bigger issues with the driver simply wasn’t going to happen it was probably worth making some other improvements for the time when that does happen.
It has been known since system11 acquired a PCB and made a video that there was a graphical effect missing in Takeda Shingen, A Mametesters report was created with 2 handy videos demonstrating the effect in Takeda Shingen and the P-47 test mode.
This was a while back, and in the meantime the Final Burn Alpha devs emulated the effect due to having more active devs on the MS1 driver than we have.
Since nobody else had done it yet, and it was easy enough, I ported the FBA code that dink and iq_132 had written back into MAME; since the FBA code was based on the MAME code in the first place this wasn’t too difficult.
The result can be seen in the vidoes below. Note, I’ve used the English language set ‘Shingen Samurai-Fighter’ instead of the Japanese language set system11 used for his video. Also note, the game really is broken beyond being playable in MAME right now and crashes out at the start of level 2 even in this test video. The effect can be seen after I pick up the power-up which turns my sword into a flashing one, and then kill some enemies, with the effect emulated they ‘pixelate’.
The P-47 test mode video demonstrates more clearly the settings for Mosaic that are available. (same settings as Mametesters reference video have been used, you can see the effect creates the same pixels in MAME)
The effect is also used on the Jaleco logo in P47, after the spinning squares, looks a bit ugly, but should be correct. There’s actually another missing effect on the Jaleco logo here, the initial graphics should draw sprite trails, we’re going to have to look into that one too, could once again be the only place it gets used(!)
Obviously these will be more interesting to you once the driver works properly again (which like I say, I have no ETA on) but until then you might appreciate seeing them anyway.