History of Computers - Cooling, Part 1, of 2

We have already mentioned the provisions for providing a backup power system including generators and battery packs [see Computer History - Redundancy]. You can see from it that we are talking about a lot of power here.

Power means heat, and in the strict world of computers, too much heat can cause a variety of problems. Manufacturers have very small tolerances on operating temperature and humidity.

In the early days of vacuum tubes, electronic circuits were more resistant to heat and most components could be designed to operate at high temperatures. For example, a resistor designed for one-quarter watt of power dissipation in a circuit can be replaced with a 10 watt resistor of the same value in the tube design and have the same effect in the circuit. Of course, 10 watt resistors are physically much larger, but space is not as important as today's circuits.

However, the problem of generating heat in a vacuum tube computer is very similar. The vacuum tube works by heating the cathode to emit electrons. The cathode has a negative charge and the anode has a positive charge.

Due to the voltage difference of several hundred volts, electrons are called anodes and can flow freely in a vacuum. This flow is regulated by one or more grids placed between the cathode and the anode. The gate has a slight negative bias compared to the cathode and can be modulated or altered to control the flow of electrons and then control the current.

For example, in an amplifier, a triode [a tube with three electrodes, an anode, a cathode, and a grid] can be fabricated by applying a varying signal [sometimes from a vinyl disk] to the grid. Its small change in amplitude or size is amplified in the current through the tube, typically measured on a resistor in the anode circuit.

But we are digressing! Go back to the computer. In computers that use vacuum tubes, they are typically used as switches, on or off, 0 or 1, consistent with binary systems. This can be easily accomplished by applying a negative voltage to the cathode to close the tube, or by applying a positive voltage to the cathode. This arrangement works well in circuits such as flip-flops and their derivatives.

But - always one but - because of the large number of circuits required, each tube generates heat to work, and the cooling problem is huge. Large blowers and cooling fans around the ducts as well as indoor air conditioners are standard. Liquid cooling is also used.

When transistors appeared, in the 1960s, each circuit generated less heat. However, as new solid-state technologies place new demands on more complex designs and capacities. The number of individual circuits is multiplied.

In addition, the tolerance for temperature changes is small. Transistors, which are also commonly used as switches, when turned on, turn on when overheated, causing system clutter.

At the time, the transistor was not a fully predictable device. They will be based on tolerance requirements and will be selected separately for this purpose. Problems can occur if the tolerance limit is approached and there is a suspicious location in the circuit or a physical location in the machine. Room air conditioning has become very important.

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

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Orignal From: History of Computers - Cooling, Part 1, of 2