Over the past few months, in a thread at shmups forum, we've been analyzing the cause why some Toaplan V2 PCBs are not recognized by the OSSC and show artifacts with some other ADC products.
Essentially, with certain games, the GP9001 VDP outputs a broken Hsync signal, and in the course, I developed a simple patch that initializes the GP9001 VDP with configuration from another game, thereby eliminating that quirk.
Dogyuun and Batsugun however use two GP9001 working in tandem, and the patch cannot be applied in an analoguous manner there: it leads to graphical errors, probably because it interferes with the teamwork between the two chips.
In a nutshell, instead of burning dozens and dozens of EPROMs trying different initialization vectors, stabbing in the dark, just to potentially arrive at the conclusion that it's not possible or to arrive at an imperfect (and as such unacceptable) result, I figured that the best way by far would be to (eventually) decap the GP9001 – since that would have to be done anyway at some point for projects like the MiSTer and MAME.
I don't have a direct contact, but I know some people who could potentially get something going or know others who could.
In 2012, Dr Decapitator (now aka. caps0ff, who in 2016 also did sound-related chips for Vimana, Teki Paki, Fire Shark and Ghox), managed to dump a set of SNES DSPs, which are a crucial component of certain game cartridges, for byuu et al., the author of bsnes (article).
Coincidentally, byuu (now called Near) is currently trying to get the two SNES PPU (= Picture Processing Unit) chips scanned.
The magnification factor of the existing scans by John McMaster is not high enough to trace all the details.
Supposing the SNES PPU effort could pick up pace medium-term, I wonder if there are some synergy effects that could be leveraged?
Essentially, with certain games, the GP9001 VDP outputs a broken Hsync signal, and in the course, I developed a simple patch that initializes the GP9001 VDP with configuration from another game, thereby eliminating that quirk.
Dogyuun and Batsugun however use two GP9001 working in tandem, and the patch cannot be applied in an analoguous manner there: it leads to graphical errors, probably because it interferes with the teamwork between the two chips.
In a nutshell, instead of burning dozens and dozens of EPROMs trying different initialization vectors, stabbing in the dark, just to potentially arrive at the conclusion that it's not possible or to arrive at an imperfect (and as such unacceptable) result, I figured that the best way by far would be to (eventually) decap the GP9001 – since that would have to be done anyway at some point for projects like the MiSTer and MAME.
I don't have a direct contact, but I know some people who could potentially get something going or know others who could.
In 2012, Dr Decapitator (now aka. caps0ff, who in 2016 also did sound-related chips for Vimana, Teki Paki, Fire Shark and Ghox), managed to dump a set of SNES DSPs, which are a crucial component of certain game cartridges, for byuu et al., the author of bsnes (article).
Coincidentally, byuu (now called Near) is currently trying to get the two SNES PPU (= Picture Processing Unit) chips scanned.
The magnification factor of the existing scans by John McMaster is not high enough to trace all the details.
Supposing the SNES PPU effort could pick up pace medium-term, I wonder if there are some synergy effects that could be leveraged?
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