I'm working on a test system emulator for the Thor Core project. It's based somewhat on the FISA64 emulator. It's a Visual Studio 10 Express project. And features reasonably fast emulation of the test system. (It reports 0.7MHz emulation rate while the real system runs at 25 MHz).
The most recent update is to support changes to the ISA for a newer segmentation model.

Anyway, I can't get the debug screen to work, it displays as blank and it's really strange because the debug screen is just an instance of a "screen" object and the main screen "screen" object seems to work. Writes to the debug screen are indeed updating the debug screen memory. If I switch the memory address to $FFFD0000 (the main screen) for debug output then the debug output appears on the main screen. So I'm pretty sure the "screen" object is working. Right now I'm trying to identify a difference in how the debug screen is setup or used versus the main screen.

Found the problem with the debug screen display. During display rendering (paint event on a picturebox) the entire form was being invalidated instead of just the display control. Briefly, invalidating the control at the end of rendering it creates a display loop which causes the next render.

Should have been

Why it worked for one screen and not the other is a mystery still.