History of the Computer – Cooling, Part 1 of 2

We have taken over the facilities to back-up power systems involving generators and banks of batteries (see history providing computer – redundancy). You can probably tell from this that we are talking about a lot of power here.

Power means heat, and in the exacting world of the computer, excessive heat can cause all sorts of problems. Manufacturers had very close tolerances for the control of the temperature and humidity.

In the early days of vacuum tubes, electronic circuits were more tolerant of heat, most of the components can be designed to operate at high temperatures. For example, a resistor designed for one quarter watt dissipation in a circuit today could be replaced by a 10 watt resistor of the same value in the tube design and the same effect in the circuit. Of course the 10 watt resistor physically much larger, but space was not as critical as in circuits referee.

However, the problems of heat were very clear in the vacuum tube computer. The vacuum tube operates by heating the cathode so that electron emit. The cathode has a negative charge, while the anode a positive charge.

Due to the voltage difference of several hundred volts, the electrons are attracted by the anode and the vacuum can flow freely. This flow is regulated placed by one or more grids between the cathode and anode. The grid has a slight negative bias voltage relative to the cathode, and can be modulated or changed to the electron current and hence the current control.

For example, an amplifier, a triode (a tube with three electrodes, Anode, Cathode and Grid) can be made by a varying signal, perhaps from a vinyl disk on the network. The small differences are amplified in amplitude or magnitude of the current through the tube, usually measured over a resistor in the anode circuit.

But we digress! Back to the computer. In the computers with the aid of vacuum tubes, they are generally used as a switch, on or off, 0 or 1, in line with the binary system. This was easily accomplished by a negative voltage to the cathode of the tube, or a positive to turn off. This arrangement works well in circuits like flip-flops and their derivatives

But -. There is always a but – because of the large number of required circuits, with each tube to generate heat to work, the cooling problems were enormous. Large blowers and cooling fans around the tubes, as well as room air conditioning were standard. fluid cooling was used as well.

When transistors came along, in the 1960s, there was less heat generated per circuit. However, with the new solid state technology came new requirements for more sophisticated designs and capacities. The number of individual circuits multiplied.

It was the lower tolerance temperature. A transistor, also commonly used as a switch, can be switched off when assumed, as they get too hot, causing chaos in the system.

A transistor was not perfectly predictable device at that time. They would behave properly within tolerances, and they were individually selected. When close to the tolerance limit and a sensitive place in the circuit or physically in the machine, a problem may arise. Room air conditioning became very important.

In Part 2 we will look at conditions in the computer room.

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