Reply To: OSSC for PCBs

#27639
Harrumph
Participant

Regarding 390, see my old post here:

Tips & Tweaks: Lx3, Lx4, Lx5 modes

Basically, when normalizing the signal for square pixel displays, all various horizontal total widths are converted to multiples of (roughly) 390 (at 59.94/60Hz framerate).

More examples related to your PCBs (note massive use of integer rounding below, numbers not exact):
Square pixel definition: 6.14 MHz = PAR 1 (derived from rec 601 ntsc video, half rate of 13.5 MHz with 10:11 PAR)
NeoGeo 6.00 MHz = PAR 45/44 (i.e. 6.14/6.00); convert samplerate: 384*45/44 = 393
Toaplan2 6.75 MHz = PAR 10/11; 432*10/11 = 393
Espgaluda 10 MHz = PAR 0.614; 640*0,614 = 393

Edit: Note that these have slightly higher value per line, as they all have lower framerate than NTSC video. I guess in this case it would be more appropriate with multiples of 393…