Retrotechtacular: TOPS Runs the 1970s British Railroad

How do you make the trains run on time? British Rail adopted TOPS, a pc system born of IBM’s SAGE protection challenge, together with work from Standford and Southern Pacific Railroad. Earlier than TOPS, operating the railroad took paper. Plenty of paper, starting from a prepare’s historical past, assignments, and all the opposite bits of knowledge required to maintain the trains transferring. TOPS stored this knowledge in real-time on pc screens all throughout the system. Whereas British Rail wasn’t the one firm to deploy TOPS, they have been actually pleased with it and produced the video you’ll be able to see under about how the system labored.

There are quite a lot of photos of previous huge iron and the narrator says it has an “immense storage capability.”  The precise computer systems in query have been a pair of IBM System/370 mainframes that every had 4 MB of RAM. There have been additionally banks of 3330 disk drives that used detachable disk packs of — gasp — between 100 and 200 MB per pack.

As primitive and huge as these disk drives have been, they pioneered many familiar-sounding applied sciences. For instance, they used voice coils, servo monitoring, MFM encoding, and error-correcting encoding.

The software program was written in BAL, the IBM meeting language, though there have been a set of macros referred to as TOPSTRAN to make it barely simpler. Initially, every depot was going to get an IBM card reader and punch machine, however these proved to be unreliable within the rugged atmosphere. As a substitute, every depot had an emulated card reader and punch utilizing a Datapoint 2200 — the well-known pc that didn’t use the Intel 8008, however that CPU was made for use on this pc.

Within the video, you’ll be able to see some Datapoint 2200s and card readers in use again on the knowledge heart. They even take the duvet off one of many Datapoints across the 3-minute mark. The machines had 12K of RAM (on three circuit playing cards) and two tape drives. Across the 24-minute mark you get a take a look at a 600 baud, though the railroad apparently solely used 200 baud for reliability. In addition they present a 2,400 baud modem that, we’re fairly certain, needed to be tuned earlier than use.

The video can’t appear to determine whether it is for basic audiences or technical folks. For instance, it describes the tones from the modem and exhibits block diagrams of most of the methods. There are even some faux oscilloscope traces of modem outputs.

So far as we are able to inform, a few of TOPS remains to be in use at the moment. We hope a few of it has been modernized, although. Should you like Nineteen Seventies mainframes, we’ll go forward and waste the rest of your day. No kidding. The video doesn’t embed, however you’ll be able to play it by clicking the picture below.