Wow! You were right on the money! It was indeed PD21! I must have damaged the trace below the IDE header earlier in the build and after many cycles of handling and testing, it gave up the ghost. It took a microscope to see it. I added a bodge wire it and it is booting into TOS better than ever!agranlund wrote: 19 Jun 2025 15:08 The MFP is responsible for placing the interrupt number on the data bus D0-D7 so possibly
PD21 (mfp<->68150)
BD5 (68150<->buffer)
D5 (buffer<->cpu)
(I am seriously impressed that you nailed it to the exact trace based entirely on the error message. Who needs a scope? :lol: )

