It'll never work!

February 17, 2007

Everyone who uses computers knows they fall over a lot. Programs crash. Applications fail. You lose all your work. It's frustrating, I know. Rather than cursing however, stop to think just how amazing it is that your computer works at all.

A typical computer consists at a basic level of some sotrage, some microchips that process the stored data and some input/output stuff. Your computer probably isn't a basic one. It's probably a pretty damn advanced one if it's capable of reading this*. There's lots of ways of counting the complexity, but the chances are your computer internally has well over 40,000,000 transistors, and perhaps more than tripple that if it's a recent model. Every one of those transistors has to be joined to the rest of the system just right at manufacture. When running, every transistor works like a little electric gate (although they don't physically move). They all have to be open or closed in a very precise order and they're all interconnected and affect each other.

There's a clock inside your computer to make sure all the little transistor gates are operating in sync with each other. This clock is ticking at an almost inconceivable rate of around 3,000,000,000 times every single second (again, depending on how modern it is). The 'wires' that the chip is made up of are so thin that you could fit 1000 of them across the width of a human hair.

If any one of the 120 million or so transistors in a modern computer fails to flip in just the right way at just the right time, there's a good chance of a cascading failure that will cause millions more transistors to do the wrong things as a result of the original failure. Moreover, each transistor's behaviour is controlled by a horrendously complex series of instructions created by a human programmer. People of course are prone to making errors and programmers are no exception.

To me it is totally incredible that any computer runs for more than a fraction of a second at a time. If I had somehow never seen one working before and the principal was explained to me, I'd be very skeptical that such a thing could even be built. I'd be even more skeptical that they could be cheap enough for the average person to own, or simple enough to operate that almost anyone can learn the basics and perform useful work with them.

I'm currently using a computer that I've owned for maybe 5 or 6 years. It's been on, running, for a very large percentage of that time, and it hasn't worn out. It is no slower today than the day when I first set it up. It is no less useful now than it was when new. It usually runs in a stable way for several weeks between reboots. For such an implausible machine it works outragously unbelievably incredibly fabulously reliably. Yet I take it for granted, and even curse it when some small part of it doesn't function quite perfectly.

But then, combustion engines amaze me in the same way. Confining hydrocarbon explosions hundreds of times per second in a thin metal chamber by mechanical valves, surrounded by oil and water? Surely that would go round about twice then melt, pop, bend, shatter, burst, catch fire, shake itself apart or simply stall.

* To computer-savvy people reading this article, I know a lot of the details above aren't strictly the whole story, or are at least debatable. They're sufficiently close to the truth however to get across the amount of wonder required.


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  1. Matt says:
    February 20, 2007 @ 08:10 — Reply

    "But then, combustion engines amaze me in the same way"

    I'm begining to think that too. There are sooo many things to go wrong and yet they don't for a large percentage of the time. Someone is doing a good job somewhere. Not something you want to be thinking about while boarding a airplane!

    We rely on so many things in our life that are fantastically complicated, one of which is our own bodies. Just consider the range of different fuels we use and the lack of servicing! How we ever live for more than a few years I will never know.

  2. CMU says:
    February 20, 2007 @ 11:08 — Reply

    Yeah, absolutely. I have an article in my mind about how life copes with this stuff. Even more stunning is when it goes partly wrong but still works. I've seen a few cases recently of things like a frog with eyes in its mouth, a two-headed cow and so on. It's incredible how well it patches up the joins to still work even though those cases aren't on the organ plan that the DNA contains.

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