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With the recent release of the 1st gen cave game, dodonpachi, it has opened a laundry list of questions from me.
shmup fans are categorically the most analytical about how arcade emulation functions and how a game reacts to their movements.
to my untrained eye, a shmup game "plays" as it should, but then i read how there are little things which are not quite like a real PCB.
which leads me to think "shouldnt these FPGA recreations be exactly as an arcade?"
i think some of the problem is from the amount of people who have access to both the original PCBs and a MiSTer to compare the two.
with mainstream retro consoles, there is a much larger group of people that can compare actual hardware to the FPGA mister version, and for the most part, the popular consoles (SMS, NES, genesis, SNES, neogeo, turbografx, GB, GBA) are at a point where the hardware-to-FPGA difference in behaviour is ~99% accurate with very few accuracy issues in speed.
the fact that fewer people have original arcade PCBs and a mister to compare are, imo, what will ultimately hold back a core developer from really nailing down the behaviour of arcade games to that same ~99% accuracy of the mainstream retro consoles. im under the impression, an arcade core developer should be working close with someone who has a PCB, is exceptionaly good at the game, and understands every small piece of how the original PCB behaves and the slowdown for the game.
i bring up these FPGA accuracy concerns because MAME does exist. more notably groovymame.
with something like groovymame, which is hardware accurate in terms of slowdown for a large majority of their shmup games, the 1-frame of inherent lag from software emulation is a valid tradeoff, compared to playing an FPGA version of an arcade that is inaccurate. yes, it is cool to have all the arcade parts of the PCB FPGA'd, but thats not enough to get the FPGA core to a place where its considered 1:1 accurate to a PCB.
i do remember when CPS1 was being worked on, people were comparing the core to actual PCBs, but im not seeing this same dedication with arcade cores lately. my thought is, "if accuracy of the original hardware and preservation is the end goal of FPGA, then the majority of these arcade cores are works-in-progress and shouldnt be used for anything except educational purposes." groovymame, for all intents and purposes, can function the same if not better than their FPGA counterparts, and groovymame in particular can work to reduce the 1-frame of software lag down to single digit milliseconds and not 16ms.
this is in no way a slight against the MiSTer.
i love having these retro systems in FPGA form, and still view my MiSTer purchase as one of the coolest pieces of electronics ive bought in a very long time. but i am concerned with arcade core development as a whole, and feel like an arcade developer should be working in tandem with a person who knows the PCB and how it plays. if the general public plays an arcade core, im very sure they likely wont know the difference, but getting a consensus for arcade FPGA accuracy, in particular from SHMUP fans, is a much trickier and long winded process.
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Because for G-sync (which my monitor can do) to work, it has to be called by the GPU driver in the OS.