IBM 1620 - Photos
and Some Background Information
The IBM 1620 was introduced in 1961. The main console is on the left and contained 20K of heated, magnetic core, decimal memory. An additional 20K of memory was contained in the memory unit on the upper right, and one more 20K unit could be added. The IBM1622 card/read/punch is on the lower right. The console typewriter still had hammer keys instead of the Selectric-type ball that was to come later. A 1443 line printer (not shown) was also used, as well as two hard disk drives, but I don't remember their id numbers.

Addition, subtraction and multiplication operations were performed by a table lookup method. Division was accomplished by a division simulating program and later by an automatic division feature. I have read that it was developed by the Navy to teach computing. There's even a rumor that the US Navy called this computer the CADET - Can't Add, Doesn't Even Try.

There were two programming languages available, Fortran and SPS. The typesetting programs used at the Star were written in SPS, Symbolic Programming System, which today we call assembler language. We thought SPS was the best solution, even though Fortran was more portable. Those who had written composition systems in Fortran were at the mercy of compiler revisions, which were many back then, and memory was VERY expensive. With SPS we didn't have to worry too much about revisions and changes to the system. Sure wish we'd had a "C" compiler back then.

We had quite a bit of fun with the system. With its many console lights, it was somewhat interesting to turn the lights off in the room and just watch it work. Many interesting patterns of lights would repeat themselves at certain intervals and you could eventually know what's running just by noticing the patterns.

One interesting pattern was generated by the newsprint inventory sort program. It would read in a memory full of data, and slowly the lights would pulse as it sorted the information. As the information became closer to being in sorted order, the lights would flash faster and faster until it became a blur. And then as the sorted information was written to disk sequentially, the lights would represent that also. This was the closest I've ever seen to a computer having an orgasm. Even the ladies at the office thought it was hilarious.

We also received some programs from universities (freeware?) that put the 1620's transistors through a certain pattern. Someone discovered that when certain instructions were executed, specific radio waves were emitted. Their programs utilized progam loops containing these instructions to control the time interval of these emissions. By placing a transitor radio close to the console, and tuning it to a certain frequency, the programs would play different songs from the computer. We always wondered how this came about, and for what reason. Anyway, when the 1620 was upgraded to a faster processor, the music became unintelligible, for obvious reasons.

Any one else having anything to say about the IBM-1620 that they'd like to share, e-mail me at