UK computing museum starts reboot of 65-year-old EDSAC

Totally awesome.

Old kit needs to be rebuilt & remembered.

LEO -- a valve based computer from 1950s superior to S360 a transitor based computer from the1960s.

I think not.

Brilliant - but its more fun pramming like its 1948!

C'mon folks get unwithit http://www.davidsharp.com/baby/

Mercury delay lines

Cathode ray storage tubes

Old memory tech is mind-boggling

Reboot?

Have they actually restored it, or is this a replica? I was unaware that any significant parts of it survived.

All the same, incredible achievement!

Oh, and zdnet has a rather good picture of the new EDSAC's boot ROM (which is a bit of a mechanical phone exchange)

http://www.zdnet.com/national-museum-of-computing-opens-edsac-display-recreating-1949s-top-computer-7000036216/

The boot ROM is one of those details that makes EDSAC so brilliant. Everyone else building computers at the time thought that building an electronic computer was an impressive achievement by itself. The EDSAC team also thought through what else was needed to let other people in the university to do something useful with it - so they invented boot ROMs and subroutines and so on.

Symbolic machine code

In 1967 I started programming a Ferranti Argus minicomputer. It had a primitive assembler that alllowed addresses such as v12, v13, etc. So not a fully fledged assembler by the standards of the contemporary IBM 1620, another machine I used.

I later learned that EDSAC programs were written in a similar primitive assembler: clearly an ancesral work.

Neither EDSAC nor Argus had floating point hardware, so for science and engineering calculations you had to understand scaled fraction arithmetic. Not many people did.

Bring back the old machines

There are lessons that can be learned when you program in that environment - lessons that many modern programmers never had to learn, such as how to write "Hello World" and produce an program image that's less than 10Mb ... or an operating system that's under 500Mb (hello Lollypop).

I came late to the art of programming but I can remember the challenges of writing bootstrap code that fit into a 1702 EPROM - and the joy when I succeeded.

Imagine the OS updates they'll have to install after 65 years...

It's not the original - but it's very accurate and looking good!

Sorry to disappoint everyone - the article got one key basic fact completely wrong. This is not the original EDSAC - most of that lies at the bottom of the council tip near Cambridge.

This is a very accurate replica, created over the last 4 years by a team of volunteers from almost nothing but a series of old monochrome photographs of the original machine. Just the detective work to do that was extremely impressive.

We hope to have it running fully by the end of 2015.

Meanwhile visit http://www.edsac.org and in particular have a look at the excellent series of videos made by David Allen, who produced the BBC's ground-breaking series of educational TV programmes featuring the BBC Micro back in the 1980s, and which introduced a whole generation to computing in the UK.

Parts? Well, there ARE big warehouses full of valves - they are not the problem. But value bases (holders) in good condition are much harder to come by. And the trouble with other components is that resistors drift from their nominal value with age, and capacitors can deteriorate to the point where they are either unreliable or downright dangerous! So we use the largest, most authentic-looking, over-rated components we can find! The machine also uses about 1,000 tiny induction coils - our first challenge was to find a special winding machine capable of making these!

Authenticity is very important to the team. Compromises are sometimes forced upon us, but we try to be as faithful to the original as we can be. Our chief engineer is a stickler for authenticity!