This wasn’t much of a success.
At the time I suspected that differences between the PIC12C508 and PIC12C508A might be responsible.
That suspicion was not completely invented.
Microchip’s own documentation shows differences between the two devices, including the oscillator-calibration implementation.
But I never established that those differences caused this particular failure.
I later discovered a much more immediate problem:
my GQ-4X programmer was becoming unreliable and would fail randomly.
So this video should not be read as evidence that a PIC12C508A fundamentally cannot be used for PlayStation modchip code.
I eventually moved to reflashable PIC12F629 devices, which were much more forgiving when I made mistakes, and successfully returned to the PlayStation modchip project.
Calibration IDs, oscillator settings, all that razzamatazz…
but the dying programmer was not exactly helping!