Examining circuit boards from the Space Shuttle's I/O Processor

The Space Shuttle's five1 general-purpose computers played a critical role in each flight: controlling the engines, monitoring thousands of sensors, displaying data to the astronauts, and navigating the Shuttle. Each computer consisted of two 60-pound aluminum-alloy boxes: the box on the right is the CPU, a 32-bit processor that executed 420,000 instructions per second. These computers were designed before microprocessors became popular, so the processor was built from multiple boards crammed with simple chips and they used magnetic core memory rather than DRAM chips. The Space Shuttle IOP and CPU (AP-101B). Photo courtesy of RR Auction. The box on the left is the I/O Processor (IOP): the link between the CPU and the rest of the Shuttle. It implemented the input/output capabilities for the computer, primarily 24 high-speed networks that connected the computer to the Shuttle's systems and sensors. But the IOP wasn't just a peripheral; it was a separate programmable computer, more…