Notes

Some time ago a friend handed me a bare J11 chip. It had been pulled from some system on the way to scrap, presumably just because it was a pretty object. I don’t know how many hands it had been through before arriving in mine but a few pins were bent and it had not been static-protected. I wondered whether it was now anything more than a pretty object.

The J11 (more properly the DCJ11, aka “Jaws”) was one of the last gasps of the PDP-11 - a CMOS microprocessor implementation of the PDP-11/70. It’s two chips actually, mounted on a single 60-pin, over-wide, DIP ceramic carrier. The J11 was developed in the early 1980s and introduced in the PDP-11/73 in 1983/84. Although this was at the end of the heyday of the PDP-11, the J11 saw a relatively long production life, being produced till sometime into the 1990s. The unit here has a date code from 1987.

I had a recollection of hearing that these microprocessors had a monitor program built into the microcode. Documentation confirmed this - it’s called ODT (Octal Debugging Technique), a simple ASCII-based console monitor. In theory, if one could appropriately wire up a UART to the J11 one should be able to talk to the ODT via a serial terminal. The question was what would be the minimal hardware setup that would accomplish this. PDP-11/HACK