If you’ve never used a PDP-11 before it’s probably because you simply weren’t around in the 70s and 80s. Although they started as expensive machines only in research labs and industry, they eventually became much more accessible. They’re a bit of a landmark in computing history, too, being largely responsible for the development of things like UNIX and the C programming language. [ryomuk] is using an FPGA in combination with an original DEC J-11 to bring us a new take on this machine. (Google Translate from Japanese)
The FPGA used in this build is a Tang Nano 20k, notable for its relatively low cost. The FPGA emulates the memory system and UART of a PDP-11 system down to the instruction set, while the original, unmodified DEC chip is left to its own devices. After some initial testing [ryomuk] built a PC11 paper tape emulator to ensure the system was working which runs a version of BASIC from the era. The next thing up was to emulate some disk drives and co-processors so that the machine can run the first version of UNIX.
[ryomuk] also developed a PCB for the DEC microprocessor and the FPGA to sit on together, and it includes all of the jumpers and wiring needed to allow the computer to run UNIX, as well as handling other miscellaneous tasks like power. It’s an interesting build that gets to the heart of the early days of computer science. PDP-11 computers did eventually get smaller and more accessible, and if you want to build a modern version this build fits a complete system into an ATX case.
Thanks to [RetepV] for the tip!
Neat project. The white PCB is a nice touch. Perhaps the CPU is ceramic?
The white ceramic hybrid hosts the Control Unit DC335 & Data Unit DC334 chips, and some bypass caps. There are footprints on the bottom of the ceramic package for two more chips that are never populated. They would have implemented the Commercial Instruction Set or another specialized extension set.
The Tang Nano 20k is super underrated.
Shout out to yrabbit on github for doing such amazing work on the GoWIN devices
I would have thought there would be PDP-11 single board or single chip processors available commercially still. Either new old stock DEC or iron curtain/east asian knockoffs. I haven’t seen one in the wild for a long long time, but given how reluctant manufacturers are to upgrade control systems, I would think they’re still in use somewhere.
I did a quick look and I see that’s not the case.
Yes, it’s called PIC16. They’re directly based on PDP-11 architecture.
Does it have the same sensitivity to voltage fluctuations as the PDP11/23. The authentic experience is critical.
Uh..No. not even close. A few significant differences
PIC 16 PDP11
RISC. CISC
HARVARD ARCH. Von Neumann
8-bit. 16-bit
8k mem 64k+ memory
What? Elaborate? I cannot find details on this.
I’m having trouble understanding this sentence, but maybe it’s just me not being a native speaker. Neither English nor Japanese, FWIW ;-)
I don’t think it is just your English. I’d like a few more details to unpick the statement.
It’s all beautifully explained on github.
Hell yeah! I’ve been holding off doing something with my DC J-11 chips! This is a very neat solution!
If it’s V1 isn’t it called Unics? I thought that was it’s original name and it was renamed to Unix later.