There’s a lot of debate over which of several contenders was the first modern computer. One of those first operating computers was the University of Cambridge’s EDSAC — the brainchild of Dr. Maurice Wilkes. The EDSAC scored a lot of firsts and used a serial data path along with mercury delay line memories. Over on, [David Boucher] wanted to simulate the EDSAC in a much smaller form factor than the original room full of racks.

As you can see in the video below, he succeeded in that task, using a Teensy and a small LCD display. We’re reminded EDSAC was among the first machines so some of the terms we would employ were not in use yet. An order is an instruction, for example. Initial orders are akin to a bootloader.

You think of computer sounds as a modern thing, but the EDSAC had a speaker connected to the sign bit of the accumulator and operators could hear programs in operation. With time, they could recognize certain things about a program’s execution based upon the sound.

You can see some vintage 1949 programs running deliberately slowed down because the new hardware can run much faster than the original. We are guessing there’s no mercury in the replica, neither did he original machine have a 3D printed case.

If you want to know more about EDSAC, there is a wealth of information out there and we’ve covered it before. If you don’t want to build, you can run EDSAC in your browser.