Okay, so it's been 5 months since I updated this blog. I have some catching up to do!
First, it turned out that the CDC 161's auto disconnect was working just fine. We misunderstood how the software in the CDC 160A interacted with the I/O subsystem: when we thought we were checking the status of the keyboard input, we were actually requesting it to read another character. This is why we had to hit Return twice. Doh!
With the Computeriter Emulator working pretty well, I make the mistake of asking what software we were going to run on the CDC 160A at VCF West. The answer I received: "I don't know. Hadn't thought about it."
Well, gee.... we're two months out from the show. We had a Fortran II compiler no one knew how to run, no assembler, an untested software emulator for the CDC 160A, and no idea for what the demo should be.
The main criteria were that it should entice attendees to interact with the computer, but not encourage them to stay for more than 5 minutes or so. I wanted to implement Wumpus, but that failed the second criteria and probably would take too long to implement. The museum has a near obsession with Tic-Tac-Toe so I suggested that, and that was accepted.
Rather than let this turn into a total rant, here's a list of things I did to create the demo:
- Identified the vasm retargetable assembler as a viable basis for a CDC 160A assembler.
- Retargeted vasm to accept CDC 160A nmemonics and generate object code.
- Wrote a Linux utility to download software binaries through the CDC 161.
- Wrote a CDC 160A assembly program to accept binary downloads via the CDC 161.
- Wrote a Tic-Tac-Toe game in CDC 160A assember, loosely based on this article.
- Added the CDC 161 typewriter to the CDC 160A emulator software.
- Identified and corrected several errors in the CDC 160A emulator software.
- Wrote a CDC 160A assembly program to punch bootable paper tapes
Did I mention that the computer had to be disassembled in mid-July so it could be trucked to California?
I also proposed giving a talk at VCF West, which the event organizers accepted. In preparation for this I researched the history of the CDC 160A and created a presentation using LibreOffice Impress. This presentation was recorded, and when it gets posted to Youtube I'll add a link here.
In the end, the Tic-Tac-Toe game was a big hit among attendees. And with Dave of the "Usagi Electric" Youtube channel, who dropped by last week and wanted to chat about the CDC 160A:
