Start of something new & daft

I’ve long had an interest in computers, older computers that is. I mean I grew up in the 80s and that was the era of computers, I had a VIC20, C64 and so on. But what was missing was the blinking lights, which was part of the idea behind the PJ5CPU project (Under the TTL CPU category).

Now I also like obscure things and the DEC DCJ11 CPU is one such chip, it is essentially a PDP11 on a chip minus the RAM and peripherals (floppy disk, hard disk, serial, etc), I’ve been after one for a while but didn’t know what I’d do with it, anyway one came up cheap on eBay so I grabbed it;

The white is ceramic and it looks even more stunning in real life. So, now I have one, what on earth am I going to do with it?

Well whilst chatting with people on the Usagi Electric discord about this chip, I had the daft idea to make a PDP11 style based CPU that would interface with the PiDP11 panel.

What is a PiDP11? Well it’s a PDP11 panel with a raspberry pi behind it emulating a PDP. Oscar has done an amazing job with the plastics and the PCB.

So, I’ve been following the PDP11 Hack page, and reading some of the datasheets and manuals for the DCJ11 chip, and come up with this schematic.

Next is to layout the PCB where I’ve put an LED on everything (80 in total). Assuming that works a second revision of PCB will be made with more memory, some ROM and a few other bits and bobs with the intention of hooking it up to the PiDP11 panel.