The issue is that this was a thing years ago, several boards were shipped and it worked flawlessly, even with almost instant loading times, you really couldn't ask for better.
I'm kind of angry as I've been digging a bit and it seems like there were some people who reached out to aje_fr asking if he was interested in mass producing them and it looked like he turned them down.
Now we have a great project getting dust and, sadly, slowly descending into oblivion, to the point where people will just forget about it.
I know Darksoft has a board and, despite how people get triggered just reading his name here, at this point I hope he reverse engineer it and starts producing them.
Maybe he's working on a CPS1 multi, who knows.
There are several issues to overcome to make a proper CPS1 flash board.
First, you need a donor C board, as it does some important graphics work apart from protection. I guess the current cps1 multi redirects the programmable addresses to the proper ones based on the C board model, and if the C board is an old one without multiply protection, computes the values itself.
Then, there are several revisions of the CPS1 mainboard, some run at 12MHz and some at 10, so you need a "good" one if you want to play all the games.
And finally, there are the CPS1-Qsound games, I think that multi runs bootleg versions with the sound program running on the standard cps1 hardware, that is crap compared to the qsound hardware quality.
So, in order to have it working properly for all games, you'll need a "fast" cps1 A board, with the qsound board (that combo is ultra rare and expensive), then a working game that can donate the C board, and just replace the B board with the multi. That's not a good approach.
That is of course if you want a perfect quality multi, if you just want one that plays older games, and the qsound ones with crap sound, then an standard board is enough.
So a good quality cps1 multi should contain, apart from the hardware for the rom data serving, a C board emulation, and qsound hardware emulation. Still you will require one of the latest A boards with the fast 68k, but that's more manageable.
Ah, and also it should have a proper menu
