root42 wrote on 2020-05-25, 11:38:

Pierre32 wrote on 2020-05-25, 11:03:

Yep, my motherboard (Asus ISA-386C) has such a jumper. It's labelled MONO/CGA, but the data sheet actually says position 1 is EGA/VGA/MONO, and position 2 is CGA. In any case, this had no effect on the behaviour for me.

The card (which is Tseng, not Trident) has a solitary jumper on it labelled D/E. Not sure what it's for, and swapping it didn't change the behaviour.

I'm not able to test the card in another machine right now, but will be interested to try that when I can.

Those jumpers mostly determine which memory address the video card is supposed to appear at: 0xB800 for color cards and 0xB000 for mono MDA cards. Maybe also if a BIOS extension was to be expected (EGA/VGA). I am wondering though why your board puts mono and EGA/VGA into one basket...?

Yeah it seems weird. My reference is from TH99:

Pierre32 wrote on 2020-05-25, 11:43:

Yeah it seems weird. My reference is from TH99:

Capture.PNG

Maybe it's for 40/80 column modes? But even CGA can do 80 column with 640x200...

Pierre32 wrote on 2020-05-25, 11:03:

The card (which is Tseng, not Trident) has a solitary jumper on it labelled D/E. Not sure what it's for, and swapping it didn't change the behaviour.

Most likely to Disable/Enable IRQ.

As for the COLOR/MONO jumper on a motherboard, I suspect it's to select the primary display when two cards are installed.