I did a test on a new modeline for everything above x241 up to x288 in mame.ini, and forced the refresh rate to ~48.3Hz. I also disabled interlace in mame.ini.
I got this value (48.3Hz) playing with ArcadeOSD and 400x288 resolution (unlocking dotclock and reducing the frequency on the vertical geometry so that the image became centered vertically)
You don't always adjust refresh rate to adjust vertical centering, right? Vertical centering can be better adjusted by removing lines from the vertical back porch and adding back the same number of lines to the vertical front porch, and vice versa. This method can be used to adjust vertical centering without any effect on refresh rate.
If you're already aware of all this, and you had actually reached the limit of adjustment with that method, you might be able to get a little more out of it by increasing the total lines (v total). Doing that will also drive down refresh rate, but you can counteract that by raising horizontal scan rate through adjustment of the dot clock. Of course, raising horizontal scan rate can only be taken so far before you start losing sync, and may affect horizontal size, which can be counteracted by adjusting total horizontal width (h total).
Here's another thought, I bet you have more vertical position adjustment available via front/back porch changes with your 60Hz modelines. Try changing vertical position in the service menu to best fit your 288 line modeline, then bring the others back in line with front/back porch changes.
Ultimately, you'll never get a 288 line modeline all the way up to 60Hz, but I bet you can do a bit better than 48.3Hz while maintaining your vertical centering.
The larger problem is that you're using one modeline for way too large of a range of vertical resolutions. Why not add two 256p modes? One at 55Hz for R-Type and one at 60Hz for commando, Donkey Kong, etc. This will allow you to use syncrefresh with all of your 256p games.
If you have trouble getting 256 lines up to 60Hz, try doing it with the fewest number of total lines and highest horizontal scan rate as possible.
Keep the 288 line modeline for games that actually need 288 lines, and bring up refresh rate as much as you can. With this modeline, maybe try waitvsync instead of syncrefresh to fix the tearing without linking game speed to refresh rate.
rCadeGaming,
Thanks for these excellent tips!
I didn't have much time to test everything, I'll try to answer all suggestions next Sunday (time is really an issue for me :-) )
I created a new modeline for x256, here are the 4 modelines in my mame.ini
crt_range0 15376-16462, 48.30-65.00, 2.748, 5.496, 8.244, 0.061, 0.182, 1.552, 0, 0, 192, 224, 0, 0
crt_range1 15376-16462, 48.30-65.00, 2.245, 4.489, 7.482, 0.061, 0.182, 1.552, 0, 0, 225, 240, 0, 0
crt_range2 15376-16462, 58.00-65.00, 1.028, 6.170, 6.170, 0.061, 0.182, 1.335, 0, 0, 241, 256, 0, 0
crt_range3 15376-16462, 48.30-48.30, 2.934, 4.890, 7.824, 0.065, 0.194, 1.619, 0, 0, 257, 288, 0, 0
With x256, commando, dkong, 194x and rtype are with a better refresh (~60Hz), with acceptable vertical overscan (Mario always appears complete in x256, only High-Scores and Credits cut in half, no problem with that, same for commando and 194x, rtype will be not centered in 55Hz, in 58Hz I see half of the word "beam", looks good). So, one more battle won! I think it's better like this than with x288 (big vertical black borders).
I tried changing waitvsync, but I didn't notice any difference.
Changing refreshspeed from 2.0 to 1.0 improved the speed for rtype (was arround 103% and now is 100% with a refresh of 58Hz).
Pac-Mania still doesn't look to fluid... but it's 48.30Hz... at least it's progressive and fits the whole screen. Pac-Man and Ms. Pac-Man look great.
Last time I arranged the values for x288 I didn't have any possibility of increasing the frequency (48Hz is the refresh that allows me to center x288), but I'll go back again to see if I did try what you suggest (I think so, but I'll do it again).
I'll do some more testing Sunday (I hope!) and post some results and screenshots.
Just a thought of mine: I remember playing all MAME games in 1998 (when I started our hobby) in 640x480, on a 15'' CRT Monitor, and a PS/2 keyboard.
I was happy then!
Never thought I could improve so much the Arcade experience like today, thanks to the 15KHz tweaks and MAME developers (thanks Calamity and SailorSat, and all guys from mamedev), and all help from this Forum.