First generation - WITCH & EDSAC

When computers were few but big!

In the largest gallery in the museum, you can see just how big those early systems really were. There's the Harwell Dekatron aka WITCH computer from the early 1950s and the ongoing reconstruction of EDSAC that dates back to 1949.

Whenever families with children visit, they are always amazed just how big the systems from the 50s, 60s and 70s really were. Their only knowledge of computing might be the PC or laptop they have at home, or the iPod and mp3 player in their pocket (which has many times more processing power than all the systems on display). We have also had many complimentary comments from those of yesteryear who actually worked on or maintained the systems on display, and are often amazed that we have them working.

Harwell Dekatron computer aka WITCH

The world's oldest original working digital computer

In 1949 plans were drawn up for a machine to automate the tedious work performed by teams of bright young graduates using mechanical calculators. Simplicity, reliability and unattended operation were the design priorities. Speed was of a lower priority.

This pioneering computer first ran in 1951 and by 1952 was using 738 Dekatron tubes for program and data storage, relays for sequence control and valve-based electronics for calculations.

It was used at Harwell until 1957, when it was won by Wolverhampton and Staffordshire Technical College (later becoming Wolverhampton University) in a competition for colleges to see who could make best use of it. It then became known as the WITCH (Wolverhampton Instrument for Teaching Computation from Harwell), and was used in computer education right up until 1973.

After a period on display at Birmingham Museum of Science and Industry, the computer was disassembled and stored at Birmingham City Council Museums’ Collection Centre.

In 2009 the machine was spotted dismantled in storage by TNMOC volunteers and a plan was made to bring it to TNMOC for restoration in full public view. Here is a BBC video of the WITCH arriving at TNMOC in September 2009. When restoration is complete, it will be the oldest original working digital computer in the world.

A tortoise not a hare The Harwell computer was pitched against a human mathematician to check the machine’s operation. The human kept pace for 30 minutes, but then retired exhausted as the machine carried on remorselessly. The computer once ran unattended for ten days over a Christmas/New Year holiday period.

You can follow the technical story of how the Harwell Dekatron / WITCH computer was restored here.

It was rebooted on 20 November 2012 to became the world's oldest original working digital computer. BBC video for the reboot

Because of its age, we can't always guarantee that the Harwell Dekatron will be working when you visit, but you'd be unlucky if it wasn't!

The WITCH Reboot - 1 minute version

The WITCH Reboot - 21 minute version

EDSAC

The EDSAC Replica Project aims to reconstruct one of the most important early British digital computers.

Designed in 1947 by a team lead by Maurice Wilkes, the original EDSAC computer operated for almost 10 years, starting from its first successful program run on 6th May 1949, at the Cambridge University Mathematical Laboratory.

The goal is to have a working reconstruction of EDSAC as it was in May 1949, built and operational in late 2015.

The full story of the EDSAC reconstruction is here.