Computeriter Emulator wrap-up

Okay, so it's been 5 months since I updated this blog. I have some catching up to do!

Spoiler alert: I did get everything working in time for VCF West. Here's a pic of the CDC-160A system on display in sunny California:

 

What did it take to get it done? I pretty much lived and breathed for this project from mid April through early August. But let me catch you up on what you missed.

Mission: Emulate a Soroban Computeriter

In the early 1960s a company called Soroban Engineering produced a product they called a Computeriter. This was an IBM electric typewriter, modified with an electro-mechanical encoder to allow a computer to sense what keys on the keyboard had been pressed, and solenoids to allow the computer to operate the keys to print text.

This photo is taken from a Soroban technical manual, available on the Bitsavers archive here. It shows the IBM typewriter and the coder and decoder modules Soroban added to create the Computeriter.

Although not as heavily built as the Teletype machines of the day, the Computeriter could print 26 upper case and 26 lower case letters, ten digits, plus 24 special glyphs. This is the device Control Data Corporation (CDC) chose as a base for their CDC 161 Typewriter Unit for the CDC 160 computer.

Unfortunately, the Computeriter in the System Source Computer Museum's CDC 161 is badly worn. A typewriter restoration expert brought in to consult advised that attempting to refurbish the most badly worn part, a drive roller, would cost over $1,000. Even then, he said his experience was there was only a 50% chance that the refurbished roller would function properly. So the museum management decided to replace the electro-mechanical Computeriter with a custom electronic device that would allow the use of a more modern terminal or laptop computer with the CDC 161 electronics.

What have I been up to?

Last summer I came across my somewhat tattered copy of the PDP-11 Processor Handbook. This dates to my first job as a software engineer in the early 1980s for EMC Controls. EMCC was a process control system manufacturer whose products ran everything from bakeries to steel mills to the Trans-Alaska Pipeline. A descendant runs the ventilation systems for some of Boston's road tunnels.

I got hired there because they used Intel 8080A microprocessors in their EMCON-D2 process loop controllers, and a friend of mine who worked there knew I knew a lot about the 8080A. My first day I was informed they didn't have an immediate need for work on the 8080A software, but would I like to do a sysgen on a PDP-11/44? I replied, "What's a 'sysgen'?" I never touched a single line of 8080A software in the two years I worked there, but became something of an of an expert on the RSX-11M-Plus operating system.

My first big project was the continuous annealing line for Bethlehem Steel in Burns Harbor, Indiana. It used a PDP-11/44 as a supervisory computer, which ran a mathematical model of the system to update process loop controllers. My second big project was porting the company's EMCON-D3 software to a VAX-11/750 running VAX/VMS. It was my knowledge of RSX and VMS gained at this job that guided my career through 1999. But that's a story for another time.