brettp11 wrote on 2021-12-24, 13:44:

Hi! You guys have saved me many times before so I was hoping for some help here.

I’m trying to boot King’s Quest 1 (Tandy / IBM PC Jr) on my retro 486. It will boot and actually play but the screen is garbled and flashing (see picture). Any advice?

I recently switched out motherboards with the exact same motherboard QDI model but went from AMIBIOS to MRBIOS. That was the ONLY change. It worked with the AMIBIOS QDI motherboard but doesn’t seem to work with the MRBIOS one.

That's strange. A game that uses the enhanced (for the time) graphics modes of the Tandy / PCjr systems will not work on anything else unless some layer of compatibility/emulation is added. Broken "graphics" where the screen stays in text mode is common for software that tries to set a video mode that is not supported by the system. So I'm not that much surprised it doesn't work with your new motherboard, but it is surprising that it worked with your old motherboard.

Possibly the MRBIOS looks more like a tandy system than the AMIBIOS, and with the AMIBIOS King's Quest automatically detected the unavailability of Tandy stuff and downgraded to CGA mode, which is common between PCjr and modern PCs.

This is kind of a reach, but did you check the mono/color jumper on the motherboard? If it has one, try setting it the other way.