The USSC90: the Central Processor Unit.


The Central Processing Unit.

The powersupplies.

The physical properties.

The CPU was about 2.7 meters wide and 1.75 meters high and weighed about 1600 Kg. On the right was the operator-console located. On this console 42 lamps displayed the content of one of the 4 registers. Also there were control-switches which allowed the operator to start and to stop program-execution or to execute a program step-by-step. Underneath the console there was a table with a numerical pad. This pad was the only system to enter instructions or numbers into the registers. Debugging programs was complicated. One had to execute the program step by step, checking the content of the registers as desired. When the operator had to change a number or an instruction in memory, the new number was typed into rA. Then an instruction to store (rA) in memory, was typed into rC and the operator executed this instruction in the one-step-mode to write the word in rA to the desired address.

The voltage-monitoring-panel.
The voltage-monitoring-panel. On top of the console there was the voltage-monitor-panel with the fault-warning lamps and a voltmeter. Normally, operators would never try to find or to repair hardware-failures. But we had to. In a days work with the USSC we never knew whether we would be busy processing, programming, debugging or that we were reading the manual with logic drawings or the blue-prints with circuit-schemes, trying to detect the location of a new hardware-failure. Our USSC was the last one in action in the Netherlands, therefor we inherited the complete stock of spare parts and documentation of the Dutch Univac cooperation. Most parts of our computer we had in stock at least twice. And we needed them, because when our USSC90 got older, more and more defects occurred. In the right hand part at the central unit, the power-supplies were located. Behind the console was the magnetic drum located and the 700 KHz/1000 watt transmitter, powering the 1300 ferractor-circuits. The right lower-side was occupied by a 50 cm high aluminum box, containing a large fan, blowing air into the shelves on the left to cool the circuit-boards. This part contained of two 'back-warded' bays, in which the 1700 circuit-boards were held. The front-bay could be opened forward like a door, giving entrance to the wiring inside. The front-bay contained the processor- and memory logics. The back-sided-bay which was rigid and contained the I/O-circuity.
Cardreader and CPU.
The controlpanel of the CPU.


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