Data General Nova 1200 Core Memory

One of the earlier Data General machines was called Nova 1200.
 https://en.wikipedia.org/wiki/Data_General_Nova
They were released during the first half of the 1970:ies.

One of the earlier Data General machines was called Nova 1200. You could buy memories of two types, if I remember correctly, 4kw or 8 kw. "kw" at that time meant kilo word so it was double that number in bytes since the word was 16 bits. When they failed they could be really flaky. We swapped the address driver chips and put the board in a chassis where the voltages were lowered almost a volt and the ran memory test during one night. The next night we did the same but increased the voltage to almost a volt above the specs. If it passed, we put in on the spares shelf and grabbed the next faulty board. The customers never saw a new spare part. They were all "refurbished".

Ther 16kw memories for the Nova 3 had potentiometers, making it possible to adjust the flanks and width of the pulse turning the cores around. Could be nice but the backside is that a potentiometer is not as stable as a fixed resistor. Turning an iron core up or down or on and off or whatever you say, was sort of still being left in the analog world so they must have had problems in the production, tuning them. I remember we had one of those boards where the test voltage went up a bit more than anticipated and all the address drivers around the edge of the stack popped like popcorn. We could look down on the silicon in each DIL package and see the tiny gold wires connecting the pins to the chip.The strange thing was that after cooling, the board still worked perfectly. We couldn't swap it at a customers site though :0)

When i see these memory boards I think about the little Asian ladies, sitting and threading the copper wires through the minute iron cores. That must have been a hard day's work. Well, it's so long ago that one could see each element storing one bit in the computer memories with your eyes. To see the innards of today's memories you'd need an electron microscope...