How much energy does a computer use?

How much energy does it take to power your computer?
12 March 2018

Interview with 

Jeffrey Salmond, Cambridge University


How much energy does a computer use? Chris Smith asked research software engineer Jeffrey Salmond...

Jeffrey - Ours is the biggest UK academic computer so it’s quite large and it‘s about 70th in the world or something like that. So it’s big, but it’s not the biggest.

Chris - When one goes about commissioning or building a computer, how does it work? What do you do to make one?

Jeffrey - Probably the most important bit that makes it a supercomputer, rather than just a computer, is that we have these many computers operating together to solve one problem all at once, which means that they need to have a fast network to connect them together.

Chris - When you say you’ve got them all working together, if it’s one problem how can you distribute the problem among lots of computers in that way?

Jeffrey - That’s a difficult thing. That requires a lot of work both on the hardware level and from the people writing the software to run on these computers.

Chris - Say I want to simulate the Universe, why is it better to have supercomputer like yours to do that than just my desktop PC?

Jeffrey - To simulate something as big as the Universe, you’re going to need a lot of memory. Your desktop might have a few gigabytes of memory, where's our large computer will probably have multiple terabytes of memory and you can use all of that at once.

Chris - But critically, will your computer do Facebook?

Jeffrey - It probably wouldn't actually.

Chris - That was a slightly daft question but what I’m getting at is, is the operating environment that is running on your computer different to what one would be familiar with if you just use Windows or Mac or something?

Jeffrey - It doesn’t run Windows or Mac, but it does run Linux which is a bit more niche. It can be used as a desktop environment just like Windows can.

Chris - How much more efficient is using a supercomputer than using a desktop because one way I could, I suppose, solve a problem is I could just persuade Tim and a few other people in this room to lend me their computers and link them together like you have. We could distribute our problem around the world in that way because people do do that don’t they? IBM does this with the community World Grid, I think it’s called, isn’t it?

Jeffrey - Yes.

Chris - Why have a supercomputer like yours then?

Jeffrey - Some problems: I think the folding at home problem is a famous example that was easily read over a worldwide network of Playstations in this case. But they were able to do that because each unit of work which, in this case, was calculating how a protein folded was easily separated from each other unit of work. You can simulate how protein A folds independently of how protein B folds whereas that’s not true of all simulations.

If, for example, you’re trying to simulate the weather, the weather here in Cambridge is going to be very closely related to the weather in London. If computer A is simulating the area that’s Cambridge and computer B is simulating London, then those two need to be able to communicate together very efficiently.

Chris - How do you keep them safe in the sense that are you a target for people hacking and either trying to steal what you’re processing, or steal your computing time so that they could get your very good computer to solve a big problem for them that might give them a lead in making some bitcoins, for example, that on vogue at the moment, isn’t it?

Jeffrey - The supercomputer would be an excellent resource for getting lots of bitcoins, so we do have to be quite mindful that people would like to do that. Anything in the University is under constant cyber attack by people from around the world. Our facility is no different from anywhere else.

Chris - You don’t get tempted to mine for a few bitcoins yourself?

Jeffrey - Not yet.

Chris - Not that you’re willing to admit on air anyway...



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