Ok, we’ll admit it. If you asked us what the first transistorized computer was, we would have guessed it was the TC from the University of Manchester. After all, Dr. Wilkes and company were at the forefront and had built Baby and EDSAC, which, of course, didn’t use transistors. To be clear, we would have been guessing, but what we didn’t know at all was that the TC, with its magnetic drums and transistors in 1955, had a second life as a commercial product from Metropolitan-Vickers, called the Metrovick 950. [Nina Kalinina] has a simulator inspired by the old machine.The code is in Python, and you can find several programs to run on the faux machine, including the venerable lunar lander. If you haven’t heard of the Metrovick, don’t feel bad. Oral histories say that only six or seven were ever built, and they were used internally within the company.It seems hard to imagine now, but in the 1950s, transistors for computing were actually a disadvantage. The devices were slow. The TC, for example, used old point-contact transistors (200 of them) and 1,300 point diodes. The Metrovick 950, mercifully, used more modern junction devices. You might think that transistors would be more robust, but the early devices often failed.The Metrovick wasn’t totally transistor-based. Like the somewhat newer TRADIC from Bell Labs, it used a vacuum tube to produce a clock signal with enough oomph to feed the whole machine. The first fully transistorized machine is a bit of a moving target, but is probably either the Harwell CADET, the IBM 604, or an ICBM guidance computer from Burroughs. Want to know more? You can read the original engineering report (which included the title picture).We have long been fascinated with the EDSAC and often wonder if we’d have been as smart as David Wheeler and invented the subroutine.