Emulating A Forgotten UNIX Box

The AT&T 3B2 series of computers are historically significant, being the main porting platform for System V Release 3 UNIX. Unfortunately, the documentation for these computers has been nearly lost to the sands of time. They are, however, architecturally interesting machines, and [Seth Morabito] has been working for some time on reverse engineering them. Now, [Seth] is calling it: his AT&T 3B2/400 emulator is almost complete, resurrecting an ancient machine from the dead by studying UNIX source code.

The architecture of this computer is unlike anything you’ve seen before, but well-suited to a UNIX machine. The chipset is built around the WE32100 manufactured by Western Electric, and includes a WE32101 MMU for all the fancy memory-mapped I/O. The implementation of this computer is fairly complex, with oodles of glue logic, over a dozen PALs, and various support chips for a PLL and DRAM controllers. This is computer architecture the way it was intended: inscrutable, baroque, and with a lot of fancy custom chips.

The emulator for this system is a bit simpler: you can just download and run it with simh. This emulator simulates 1, 2, or 4MB of system memory, one 720KB floppy diskette, and either one or two 30MB, 72MB, or 161MB MFM hard disk drives. Not everything is implemented so far — [Seth] is still working on an 8-port serial card and a network card — but this is a minimum viable system for developing and analyzing the history of UNIX.

Turning a Pi Into a PDP

There’s no better way to learn how to program a computer than assembly, and there’s no better way to do assembly than with a bunch of blinkenlights and switches. Therefore, the best way to learn programming is with a PDP-11. It’s a shame these machines are locked up in museums and the garages of very cool people, but you can build your own PDP-11 with a Raspberry Pi and just a few extra components.

[jonatron] built his own simulated version of the PDP-11 with a lot of LEDs, a ton of switches, and a few 16-bit serial to parallel ICs. Of course the coolest part of any blinkenlight simulator are the front panel graphics, and here [jonatron] didn’t skimp. He put those switches and LEDs on a piece of laser cut acrylic with a handsome PDP11 decal. The software comes with a load of compiler warnings and doesn’t run anything except for very simple machine code programs. That’s really all you can do with a bunch of toggle switches and lights, though.

If this project looks familiar, your memory does not deceive you. The PiDP-8/I was an entry in this year’s Hackaday Prize and ended up being one of the top projects in the Best Product category. We ran into [Oscar], the creator of the PiDP-8, a few times this year. The most recent was at the Hackaday SuperConferece where he gave a talk. He’s currently working on a replica of the king of PDPs, the PDP-11/70.

Video below.

Continue reading “Turning a Pi Into a PDP”

Hackaday Links: August 24, 2014


Remember those ‘cocktail’ arcade cabinets? The Ikea Lack table has existed for years, so why not make one into an arcade table? Raspberry Pi with RetroPie as the brains,  and an ancient 4:3 monitor as the display.

Old Unixes! Running on PDPs, Novas, and IBMs! Thanks to Simh, you can emulate these old machines. [Matt] put up a guide to getting Simh running on a Pi that includes running Unix V5 on an emulated PDP-11.

Ever wanted to run your own telecom? The folks at Toorcamp did just that, 50 lines, 10,000 feet of 1-pair, and 1,500 feet of 2-pair. There’s a facebook album of all the pics.

Remember last week when Sparkfun said they shipped 2000 Microviews without a bootloader? Make interviewed [Marcus Schappi], the guy behind the MicroView. There’s also a tutorial on how to fix the issue.

Barbie needs an exorcism.

Remember the [Lord Vetinari] clock from way back when? It’s a clock that ticks 86400 times a day, but the interval between each second is just slightly random and enough to drive people insane. Here’s a kit on Tindie that makes it pretty easy to build a Ventinari clock, or a variety of other clocks that are sufficiently weird. There’s also a martian clock that’s 39 minutes and 36 seconds longer than normal, perfect for the folks at JPL.

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