<-- Previous ^ Up ^ Next -->

This picture shows a portion of the logical processing part of the computer. The orange glow of the hot filament (heater, as tube designers refer to it) is visible in many of the tubes in this photo. There are about 2500 vacuum tubes in Colossus. To put that in modern perspective, the chip that formats keystrokes in your keyboard for your computer probably has about 2500 transistors, not counting its memory. It is probably fair to say that there is more computing capacity inside your keyboard, or mouse, or TV remote control than in Colossus. Colossus consumes about 5000 watts of electricity. During the war one would guess that people liked working in a room with Colossus during the winter with so much heat radiating from the machine. All of the vacuum tubes used in the Colossus replica are between 40 and 70 years old. They have been accumulated from discarded old electronic equipment and donated personal stashes of old tubes. They say a tube in the replica Colossus burns out about once per week.