Monster 1951 machine vs $15 BBC micro:bit: Which computer won and by how much?

Which machines triumphed in the battle between computers from the past eight decades?

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One computer is the size of three wardrobes and performed calculations to help build a nuclear reactor, the other is a tiny electronic board designed to teach children to code.

If you had to place bets on which would prove the more powerful machine, your money would probably be on the former.

However, while the first computer was built in 1951, the second was released in 2016, and in the intervening years technology has advanced so far that the supercomputers of yesteryear pale in comparison to even the simplest of modern machines.

So proved to be the case this weekend, when the 1951 Harwell Witch, the world's oldest working computer, was roundly trounced by the $15 BBC micro:bit in the Grand Digital computer race at The National Museum of Computing in the UK.

The BBC micro:bit didn't just beat the Witch, it crushed it, calculating some 6843 numbers in a Fibonacci sequence in 15 seconds, while the Witch managed just three.

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Despite the gulf in performance, the role played by the two machines couldn't be more different. The micro:bit runs on the most basic Arm processor -- more commonly found in health wearables -- and is designed to allow children to run simple programs, while the Witch handled simultaneous equations for engineers building the world's first atomic reactor for generating electricity, Calder Hall in the UK.

That said, the Witch wasn't necessarily prized for its speed, a practiced operator of a hand calculator would be able to keep up with the Harwell Computer for a time, but it could keep going far longer and more reliably than a human calculator.

"It has to be said, the Witch isn't a fast machine, it isn't the fastest of our contenders," said Delwyn Holroyd, who played a key role in restoring the Witch to working order.

"When it was built, the crucial thing about the Witch, unlike electronic machines like Edsac which were contemporary with it, the Witch was designed to be reliable, so it was slow but steady," joking its main advantage over the micro:bit is that it's not likely to get lost down the back of the sofa.

As you'd expect, the architecture of the two machines is world's apart, while the micro:bit runs on a modern silicon processor, the Harwell Witch handles its data storage and processing using a mix of gas-filled tubes called Dekatrons, valves and electrically operated switches called relays.


The tiny BBC micro:bit, held by nine-year-old Connie who programmed the board, with the massive Harwell Witch in the background.

Image: The National Museum of Computing

The exponential rise in processing power over the years was also reflected by the performance of the other machines in the race, which spanned eight decades of computing. Of the remaining machines the 1940's Facit calculator calculated seven numbers in the Fibonacci sequence, the 1965 PDP-8 calculated 16, the 1977 Apple II calculated 38, a 1981 BBC Micro calculated 70, and a 1998 Windows 98 PC managed 1477.

However, not all the computers were able to stay the full 15-second course, due to their memory not supporting a sufficient number of bits -- the digital ones and zeroes computers use to represent data -- needed to store large numbers.

A Fibonacci sequence is a series of numbers that starts with 0 and 1, with each subsequent number calculated by adding the two numbers preceding it.

Due to the disparity in the ages of the machines, instructions to calculate the sequence were input using methods ranging from punched paper tape to voice control. For example, an iPhone 6s found only four numbers, due to numbers being input using Siri voice command. Other machines ran pre-written programs to cycle through the sequence, with the winning program on the BBC micro:bit coded by nine-year-old Connie, of Christ the Sower Ecumenical Primary School in Milton Keynes.

Kevin Murrell, trustee of The National Museum of Computing and the Grand Digital race starter, said the inter-generational computing race would likely become a fixture at the museum.

"This is the first time that machines from so many decades of computing have raced together. We don't think such an event could happen anywhere else in the world," he said.

"I suspect this was the first of many Grand Digitals as we have many other original working computers, skilfully restored by our Museum volunteers, that could enter the race to demonstrate the advance of computing."

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