S/360-50 microcode held in capacitors
Curious how he got ahold of the S/360-50 microcode. On several of the S/360 models (40,50,65,67), the microcode was held in arrays of capacitors formed by large plastic sheets with conductors etched on one side of them held between large steel plates. These capacitors were quite sensitive to the pressure applied to them by the steel plates (which were sensitive to the temperature inside the machine's cabinet) and the IBM customer engineer (CE) would occasionally have to re-torque the screws which applied pressure to the plates. A microcode update required demounting the plates, replacing the plastic sheet with the new one, replacing the plates and then re-torquing them until they read properly. Model 30 used plastic 80-column punch cards inserted in slots in the machine for its microcode. Models 44, 75 and 91 were "hard-wired" for best performance and didn't have microcode, which made fixing engineering mistakes more costly. S/370 microcode was held in semiconductor memory and loaded during machine power-up initialization from 8-inch floppy disks which IBM invented for that purpose.
Biting the hand that feeds IT
