FDI drops inputs, cursor buggy on VIA C3

[AsureDawn]

Possibly related gitlab bug:
https://gitlab.com/FreeDOS/OS/FDI/-/issues/10

While the installer runs and appears to work, enter or spacebar have to be pressed repeatedly or held for 1-3 seconds before an input is accepted. When up or down is pressed, the graphics are messed up, and it is impossible to tell where the cursor is, as if the console cursor is moving in the background and messing up the UI. Same thing happens with both the 1.3 and 1.4 installers.

Edit runs fine, and does not exhibit any of these issues. So I'm thinking it must be a buggy or unsupported instruction in the C3 processor.

I've tried disabling the VGA and USB IRQs, enabling usb kb support in BIOS, masking the lower memory...probably some other things I can't remember.

The system is buggy, BIOS corrupts frequently (or so it says), but the memory is stable, it has a new cmos battery, and a good power supply.