So, this means that - and please correct me if i am wrong, as there are probably a myriad of things i am simplifying away:
a) the SNES is always run at original clock speed in non-zero delay modes
b) Even In zero delay mode the SNES is still running at original clock, but is stopped for a number of cycles after each scanline in order for the hdmi readout of that line to catch up.
but does that not lead to problems if for example a sound sample is playing and ending right before the clock is stopped, couldnt this (very small) delay lead to discontinuities (clicks, popps)?
Does this have something to do with the "Earthworm Jim (PAL)" audio problems in zero-delay mode?
I am an advocate for a special 60.09 mode - and I believe (from my own testing) that your worries about hitting that 148.5 Mhz exactly are maybe a little to strict. And even with a 148.5 Mhz Master HDMI Clock there are ways to get to that 60.09 (or even to the the exact frequency). Just some ideas, you probably already thought about:
1) Use an integer multiplier of 7 * 21,47 =~150,29 HDMI Clock - I beleive that 90%+ of TVs would handle that.
2) Keep the 148.5Mhz HDMI clock, but shorten each frame by two or three lines of vsync (in the frame sent over hdmi, not in the snes) and/or adjust hsync a little. With a little linear programming one should be able to find a combination that hits 60.09 and is still TV compatible
3) Do not use cycle stealing, but just change the 21,47 clock to run at 148,5 / 7 = ~21,214.(If all fails and we must live with 60.00Hz - at least this would prevent cycle stealing)
4) use any of the tricks above in combination to get closer to 60,09, in order to reduce cylce stealing (if it cannot be avoided altogether)
In all cases such options should come with a disclaimer and a hot-key on boot-up to restore "normal" hdmi behavior. I find the Super NT such a great system almost living up to all the claims made by analogue, but without a tearing and frame drop free hdmi mode at original speed it is not really 100%. But i am pretty optimistic that a way will be found and implemented via firmware update, if not now maybe after the dust has settled a bit.
Apart from that I found the following incompabilities:
- JP Samurai Spirits crashes after the initial Logo, sometimes the cherry-blossom animation runs for half a second before the screen blanks.
- JP Accele Brid crashes during gameplay - music continues playing but game freezes.
- JP Bakukyuu Renpatsu!! Super B-Damon lets you only use hotkeys during fades to black. As these become very seldom in game, hot-keys cease to work for long periods of time
- JP Zootoo Mahjong (my favourite Mahjong) no hot-keys at all
- Pac-Man (A&S NES Hack) graphics corruption