Cables
Cables ran in the floor and were immediately recognizable as IBM cables. They were all the same color, and, except for power, the connectors had the same look.
You did not plug IBM machines into a normal outlet. They took bunches of power. Some of them took more amperage than some houses. A little box would take 20 amps.
Your house has two phase power, about 240 between and 120 from each to ground. IBM computers ran on three phase power, 120 each to ground and a bunch of math to get something less than 240 between. Three phase is normal and you just get two phases to your house. The grid is three phase and all industrial or office buildings get three phase. The IBM stuff required three phase.
The connectors are standard from the world of electricity. Usually round hunks of metal that you screw together. These connectors were around 4 inches in diameter and up. Cables ran from the panel and the box would be plugged in. I think the power cables were attached to the boxes. The cables were thick and round, a small one was two inches in diameter.
IBM had bus and tag cables that ran from the CPU to all the control boxes. They were not daily chained, each control unit had bus and tag cables that ran back to the CPU. The cables were about two inches in diameter and had a bunch of individual conductors. I’m not exactly clear on what the cables were for but I had the idea one was for data and the other was control.
The cables ended with a plug. The plug was the same on both ends so you could put the cables in whichever way you wanted. (I read some of the doc from IBM and found that the bus and tag cables had connectors of different color on the ends, so it did mater)They came in different lengths and you got them from IBM. As part of your machine room design you did cable routing and, hopefully, ordered the right length. When you added new stuff or moved stuff around you sometimes got new cables for it. If you had a long cagle you could coil the extra up and leave a pile of cable. This took up a bunch of room and may not fit, block airflow, or cause another problem.
The connectors were rectangular, about 2×6 (really a little over 1 by 4). There were a bunch, around 40 I think, of connectors and in the middle a captive screw thing. You plugged it in, this would probably hold, and then you used the screw thing to be sure.
The cables from the controllers to the devices were particular to the device, but were about the same size. Sometimes you had a string of devices, disk drives, and they would be cabled, and attached, to each other with a cable from the first going to the controller.