I spent a lot of time in the late 70s and early 80s crammed into small computer rooms. It was an era when computers needed a room of their own, and if you wanted to use one, you needed to be in it as well. I found that invariably, there was also a middle-aged chainsmoking woman in there somewhere with you too, doing data processing.

I don't know if the job attracted middle-aged chainsmoking women, or if the job slowly morphed non-smoking young women this way over time. Whatever the case though, I endured a lot of secondhand smoke while learning to program. And so did the computer systems.

Here is where my first encounter with computer Field Service happened. One day in high school while I was in the computer room trying to extract Snoopy banner printouts from our PDP-8, a Field Service guy showed up, with a strange device. It was like a mini washing machine, full of some kind of solvent I hope was not too cancer-causing. He proceeded to grab all of our RK05 disk packs, and take the covers off them. One by one, he dropped the raw disk platters into this machine.

And it washed them.

I was amazed. And I still am. I asked about it, and he said that there was a lot of smoke and dust that built up, and that affected the life of the disks (he may have given a side glance to Mrs. Sutton, who was in the corner puffing away as she typed on the school's very dated IBM 029 card punch).

The washing machine spun and sloshed, and then the clean, dried disk was removed and put back in its case. He assured me they would work just as before, and as far as I could tell, they did. (It was after all a time before disk heads flew microns above the platter, so you could get away with exposing a disk to a dusty room. )

But I was struck by the confidence this service guy had with what he was doing. I had always considered our PDP-8 to be this priceless jewel, sitting cloistered in its own temple. You handled it with kid gloves and most often, you did not handle it directly at all. But the service tech would come in and pluck this machine apart with ease, doing what seemed to be dangerous things.

Experiences like this have a lot to do with why I became an Engineer. I ended up working for Digital Equipment Corporation, the very company whose computers I used, (and watched get lovingly washed by Field Service) as a high-school student. I worked in hardware design and engineering at the company, but I continued to be fascinated by stories from our Field Service department, and the weird situations they would get into.

Like installing a PDP-11 inside the bore tunnel for an underground nuclear test chamber. According to this story, that poor machine's job was to collect as much data as possible and send it out in the few milliseconds between the blast and it getting vaporized.

I would spend hours browsing Field Service stories in the DEC internal notes system. The "Always Mount a Scratch Monkey" story is by far the strangest, and most macabre. I never thought it was true even, but found enough backing detail about the tale to consider it, as MythBusters may say, as "Plausible".

The account of it also lived on beyond DEC to become a famous hacker meme, but I'm sharing it again for readers who may have missed this particular piece of Field Service History.

This tale concerns a lab involved with research using primates at the University of Toronto, in 1980. The Department of Medicine had been conducting experiments using monkeys, with electrodes attached directly to their brains. These electrodes and associated experiments were run using the department's new VAX 11/780, which had a superior speed to the older PDP11/05 they had been using previously, and this speed was needed due to the nature of the real-time data collection and processing being done.

The problem was though that the VAX 780 was a very new, and buggy machine in 1980. (Some of the security-related bugs were things I wrote about taking advantage of previously.) At some point, the VAX started crashing, and DEC Field Service was called. They proceeded to check the machine out by shutting down VMS and running a set of dedicated hardware dignostics tests, that exercised things like the CPU, disk, and memory.

Oh yeah. And the I/O system. That was attached to five live monkeys.

No one had bothered to tell the Field Service guy about these monkey connections, which were normally instrumented to read analog signals from the brains of the monkeys, but were also capable of generating analog voltages as output as well. A feature that was precariously (and as it turns out, insufficiently) disabled on the system.

Diagnostics being what they are, the VAX I/O system was put through grueling cycles of both reading and writing the I/O ports, resulting in voltages far beyond what was healthy being sent to the monkey brains. The monkeys all went through violent convulsions, and three actually died. In the telling of it, the Field Service guy was pretty traumatized and even threatened to call the Humane Society on the lab.

The lab itself seems also to have been doing sketchy if not unethical experiments in general and was later shut down. The whole story is pretty macabre, but as time went by, people (as is usually the case) found some humor in the whole incident.

The correct procedure when running disk drive diagnostics is to mount an unused, "scratch disk", so the contents of a valuable disk are not destroyed as the diagnostics are run. The Field Service guy had unfortunately not brought a "scratch monkey" with him that day. Advice for that later circulated through DEC's internal note system and beyond, to become the famous Field Service meme.

Today you are more likely to visit the Genius Bar than you are to have Field Service come out and look at your computer. But if you happen to have any monkeys attached to it when you do, be sure to mount a scratch one!

This article is a sneak-preview for Medium members of an upcoming edition of the Mad Ned Memo, my free newsletter covering computer engineering )and associated nerdy topics) over the past 40 years. If you like these things, consider subscribing! It is cost-free and ad-free, and you can unsubscribe at any time.