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Technology Now

Inside Britain's fastest supercomputer: Isambard AI

21 May 2026

Transcription

Chapter 1: What is Isambard AI and why is it significant?

1.364 - 4.348 Sam Jarrell

Good morning, Michael. You look like you're out on location again.

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4.908 - 13.239 Michael Bird

Yeah, Sam, that's right. I've escaped my home studio and I am standing next to one of the most powerful supercomputers in the world. How cool is that?

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14.18 - 18.425 Sam Jarrell

Wow. Okay, okay. You've caught my interest. Tell me more about this supercomputer.

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18.886 - 27.196 Michael Bird

Well, Sam, this right here is Isambard AI, the UK's fastest supercomputer. I'm Michael Bird.

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27.937 - 28.958 Sam Jarrell

I'm Sam Jarrell.

29.242 - 63.687 Michael Bird

and welcome to Technology Now from HPE. Well, Sam, I've come to moderately cloudy Bristol in the southwest of the United Kingdom to visit the most powerful supercomputer in the country. And this is a video episode. So if you want to see the supercomputer for yourself, make sure to check us out wherever you watch your podcasts, as well, of course, as wherever you listen to them.

64.004 - 79.412 Sam Jarrell

And you absolutely should, because it looks really cool. And this episode is in two parts because there is far too much for us to cover in just one episode about Isambard AI. So today we are looking at the project itself, and next week we'll be looking into how you run something of this scale efficiently.

79.452 - 85.523 Sam Jarrell

Now, Michael, when we say it's the most powerful supercomputer in the UK, just how fast are we talking?

86.026 - 103.765 Michael Bird

Great question, Sam. So, Isambard AI is a mod pod, modular data center, and it's run by the Bristol Center for Supercomputing, who have said that it is the 11th fastest supercomputer in the world and the ninth fastest for public supercomputing. And get this,

Chapter 2: How fast is Isambard AI compared to other supercomputers?

374.911 - 385.452 Professor Simon McIntosh-Smith

Should we have a look? Yeah, is that all right? Would you be able to open up one of these big cabinets? They look like big wardrobes, but inside, when I open up the doors, you'll see... lots and lots of equipment.

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385.472 - 397.296 Professor Simon McIntosh-Smith

Now, we don't tend to have the flashing lights anymore like we used to on supercomputers of old, but instead you'll see there are lots and lots of pipes, and these are pipes, not cables, and they're blue and red, and that kind of gives you a hint as to what they're for.

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397.817 - 417.694 Professor Simon McIntosh-Smith

Now, all modern supercomputers at this scale are direct liquid cooled, so they produce so much heat, so they're using so much power. But the only way to cool them down effectively and keep the thing very compact is with water. So we actually have, this is water flowing around the system. It's a water glycol mix, actually. But that's keeping it cool.

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417.734 - 427.752 Professor Simon McIntosh-Smith

In fact, the blue pipes are the cool water coming in from outside. And you'll see where that comes from later on. And the red pipes are the hot water coming back off the equipment, which goes back out to be cooled back down again.

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427.772 - 429.655 Michael Bird

So there's a temperature difference. Can I feel the difference?

429.635 - 447.045 Professor Simon McIntosh-Smith

Well, even the blue pipe is, you can, you can touch it. Even the blue pipes are warm. So in some ways it's actually warm water cooling, which I know sounds a bit like an oxymoron, but it is warm water. So it comes in warm, but it comes out even warmer. And it's just that temperature difference is the thing that's providing the cooling effect.

447.406 - 450.411 Michael Bird

And so these, these are all individual blades.

450.458 - 472.698 Professor Simon McIntosh-Smith

Yes. So these vertical, these big vertical metal structures, which if I were to pull one of those out, each one of those would have lots of GPUs on it. And the GPUs are the engine of an AI supercomputer. And there are eight GPUs on each one of those blades. And there are 55 blades in each one of these cabinets. That's 440 GPUs in one cabinet.

473.078 - 482.789 Professor Simon McIntosh-Smith

Now, they do use quite a lot of power to energize all of those. In fact, this one cabinet is about a third of a megawatt. 330 kilowatts.

Chapter 3: What makes the modular design of Isambard AI unique?

536.998 - 553.95 Professor Simon McIntosh-Smith

So very, very dense. And is the networking water cooled as well? Absolutely everything is water-cooled. In fact, you can't really tell, but it's very quiet. We're just having a normal conversation. Very quiet in here. There's a very faint hum that's going on, but that's actually from the pumps that are pumping the water in. The networking is water-cooled.

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554.11 - 558.614 Professor Simon McIntosh-Smith

Even the power supplies are water-cooled, so there are no fans in here whatsoever.

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559.535 - 565.32 Michael Bird

Yeah, I'm quite used to a screaming data center for all the fans. This is quite a nice environment.

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565.56 - 570.645 Professor Simon McIntosh-Smith

Yeah, you can be in here, but it's not noisy. We don't need ear protection or anything like that, and we can have a conversation.

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571.115 - 574.881 Michael Bird

Okay, so we have something behind us. Can we talk through what we have here?

574.901 - 589.604 Professor Simon McIntosh-Smith

Here we go. So this is, we talked about those blades, those vertical structures that we pulled out in one of the cabinets. And this is what one of the blades looks like. So it's quite long. It's surprising really just how long this thing is. And you can see there are these, interesting looking things with pipelines.

589.624 - 609.504 Professor Simon McIntosh-Smith

That's one, two, three, four GPUs here and there's another one, two, three, four on that end and the four actually group together into one server or we call them a node. This is one node on one end and another node on the other end and we've got eight GPUs in total. Down the middle is where all the networking goes. There's actually one network endpoint for each GPU.

609.745 - 629.361 Professor Simon McIntosh-Smith

So eight GPUs, actually eight network connections. Those are 200 gigabit HP slingshot for each one. So there's lots and lots of network connectivity. The pipes are where the water goes for the cooling. And the pipes are bright green. The pipes are green. Actually, the water has been dyed green deliberately in case there's a leak. which makes it much easier to spot.

629.401 - 646.983 Professor Simon McIntosh-Smith

In fact, the dye also fluoresces under an artificial light. And you can see the copper plates with the little copper pipes. It's all part of the cooling loop so that we can get the heat extracted from the GPUs into the water and outside to be cooled down again.

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