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;
![](https://www.maddox.pro/wp-content/uploads/2023/04/20230404_110244-1024x768.jpg)
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.
![](https://www.maddox.pro/wp-content/uploads/2023/04/pidp11-review.jpg)
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.
![](https://www.maddox.pro/wp-content/uploads/2023/04/Screenshot-from-2023-04-10-15-17-40-1024x717.png)
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.