www.columbia.edu/acis/history/datacell.html
Photo Illustration of Data Cell, subcell, and strip hierarchy. Photo: Introduction to IBM Data Processing Systems, IBM Textbook C20-1684, 1968. The following is from Peter Kaiser, who was in the Computer Center's Systems Group during the Data Cell's tenure: I feel you've given rather short shrift to the description of the 2321 Data Cell drive, which made such a distinct contribution to the ambient noise of the ASP-era machine room. The machine room was noisy, though after working there for a while you'd become used to it, like the ticking of a clock. The waterflow regulator and gauges were swishing, printers would be clacking and hammering, tape drives whirring and clicking, disk drives humming and making head movement sounds, and in the background (literally -- it was at the back of the room) was the distinctive THUM-SLAM-KERCHUNK-WHISH of the data cell as the cells rotated into position and were locked home, and a magnetic strip was selected and flew around the read-write drum. All of this noise contributes to one of my most cherished memories.
I was sure the runaway printer had something to do with the sudden silence, and the usual thing to do with runaway printers was to stop them with the red button, which I tried to do; The system didn't come to life after that, however, and the silence remained total. We tried to do a warm restart, but that didn't work, and finally we had to do a cold restart, losing all the queued jobs; The ultimate diagnosis was that several things had happened with just the timing to cause this: 1. An application program -- probably written in Fortran -- had spooled a line that caused the system to issue that printer the command "Skip to channel 12", which caused the printer to slew paper until it would sense a hole punched in channel 12 of the printer control tape. The system had serviced all device interrupts and was waiting in a tight loop on the only one remaining, which happened to be the one from the printer indicating it had fulfilled the command to skip to channel 12. However, the printer control tape in that printer HAD NO HOLE PUNCHED in channel 12, so that interrupt could never be serviced. Since servicing interrupts was the highest priority action for the system, and since that interrupt could never happen, the system could do nothing. Meetings were called as the center's high command tried to decide what to do about the bug, but they never came to any conclusion. As I recall, IBM acknowledged the bug but said that since it was so rare, they weren't going to fix it. In the meantime I solved the particular problem (yes, this is a pat on my own back): I went to the operators' office and borrowed the master copy of every different printer control tape, and made sure that each of them had at least one punch in every channel. But what I remember clearest is the sudden silence, not even the data cell, except for the swish of paper leaping from the printer.
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