Mastodawn

POV: #PERQ hardware debugging, as usual. The #Z80 (serving as an I/O coprocessor) is behaving strangely: fetching instruction bytes without toggling the M1 pin, jumping to random locations at around 47uS after coming out of reset; what's going on here?

Show thread

Skeezics Boondoggle

@stepleton Hmm. I wonder if this is an actual manifestation of the symptom noted in the microcode source, where "the hardware has a glitch when first starting up the Writable Control Store RAMs, the power surge can screw up the Z80". It would be interesting to watch the +5V rail during bootup to see how pronounced that surge actually is. DDS 170 at least means that maybe your DIB is okay and you can skip desoldering and testing every 74S225 in sight. For now. :-)