I am almost sure this has been asked before, but I can only find answers for NTSC: Is the IIgs capable of outputting a PAL color signal on the composite port?
I can't get it to display color on neither a LCD TV nor on my Commodore 1084S, that works perfectly for RGB. NTSC mode is in color, however.
RGB is fine for GS/OS and text, but most games look much nicer on composite. For example Prince of Persia looks much nicer on my IIe than on the IIgs.
The MC1377 chip in the GS, which converts RGB to composite, is designed to generate a PAL color signal, but the GS motherboard hardwires the MC1377 to NTSC mode by grounding pin 20 and using an NTSC 3.58 MHz clock on pin 17.
For PAL color mode, cut pin 20 to enable PAL mode, and provide a PAL 4.43 MHz clock on pin 17.
BTW, a card is in development (scheduled for later this year) that provides PAL color without modifying the motherboard.
-JB
@JBrooksBSI
Thank you for the answer, I am looking forward for this card.
I had not thought about the missing PAL clock, because I looked at the composite signal an a scope and there was definitively a color burst at the beginning. However, I did not check it for the correct frequency. And I am sure it is not phase switched either, because the mode signal is missing on the encoder chip.
Too bad that Apple was so cheap even back then that they did not throw in the couple of extra gates to provide a correct signal. At least they could have mentioned it in the manual. I think it's a bad design to leave an unusable color burst in the signal.