What's the smallest microchip we can make?

Chris Smith put this question to tech expert Peter Cowley...

Peter - Yeah, that is an interesting question. I'm not quite sure he means microchip. Let’s just do a bit of a background. So first of all, the track width of a transistor nowadays has got down to about 7 nanometres.

Chris - Transistors are the things inside chips that make the computer tick effectively, aren’t they?

Peter - Exactly, yes. Okay. So that’s not actually in production yet. They're down to about 10 nanometres. That’s about 10,000th of a human hair. Its visible light is 40 times big, wider than that with the wavelength of that. But I'm sure that’s not the question because that transistor is just on or off. What we’re probably talking about is microprocessors and I brought in something that’s about the same…

Chris - This is the gadget, isn’t it, that you said to me you'd – you brought this is in. We said at the beginning, Peter has brought a gadget in and he’s going to tell us what it is. This is a big box. It’s probably at 20 centimetres by 15 centimetres and about 5 deep with lots of wires and circuit boards. What is that?

Peter - So, this is the first computer that I developed and built as you can see, very badly built built back in 1975. The reason I brought it in is because it had a processor that had about 4,000 transistors in it called a scamp in fact. This has 32 bytes of memory.

Chris - Gosh! That’s a lot, isn’t it?

Peter - You know, you can't do much with 32 bytes of memory, can you? But I just want to compare that with modern microprocessors or microchips.

Chris - Why did you build that? What did it do?

Peter - I built it because I want to learn how to build a computer. (inaudible) necessarily want going through with it. You have to enter the – on the front side, there are some switches and you have to enter the program on these switches. There are 16 bytes of RAM so you have maximum of 16 instructions and it will switch some LEDs on, Light Emitting Diodes on, on the front. Anyway, that was just an example of that. But nowadays, we’ve got processors that have got billions of transistors in rather than a few thousand. That’s about 600, 700, 800 square millimetres and it got GPUs which are even more. But I think actually…

Chris - That’s Graphic Processing Units.

Peter - Graphic Processing Unit. The question has possibly to do with, how are we going to do in the future? Quantum computing where you’ve got multiple of these quantum bits or these are investment I nearly made down in Cambridge which was storing data of strands of DNA. Then you’ve something, then you’ve got petabyte, you’ve got huge amounts of volume of data, possibly as much as there's on the earth in the size of a bucket really.

Chris - Yeah. The DNA thing at the moment is being held back by the fact that it’s extremely expensive to make and then decode DNA and not…

Peter - Well, to write it is not – well, to read is not too bad because there have been sequences around for years. To write it is…

Chris - Yeah and to make the DNA is very expensive.

Peter - Exactly.

Chris - But people are saying it’s a bit like the sort of Rosetta stone. It’s a very long lived, very stable molecule that you could put your information in and you know it will be (crosstalk)

Peter - It will last hundreds of millions of years, exactly for long term storage.