> Considering that a Quad-core + GPU Core i7 Haswell has 1.4e9 transistors inside, even given a really small probability of one of them failing, wouldn't this b

> Considering that a Quad-core + GPU Core i7 Haswell has 1.4e9 transistors inside, even given a really small probability of one of them failing, wouldn't this be catastrophic? Yes, generally speaking it would be. Depending on where it is inside the chip. > Wouldn't a single transistor failing mean the whole chip stops working? Or are there protections built-in so only performance is lost over time? Not necessarily. It might be somewhere that never or rarely gets used, in which case the failure won't make the chip stop working. It might mean that you start seeing wrong values on a particular cache line, or that your branch prediction gets worse (if it's in the branch predictor) or that your floating point math doesn't work quite right anymore. But most of the failures are either manufacturing errors meaning that the chip NEVER works right, or they're "infant mortality" meaning that the chip dies very soon after it's packaged up and tested. So if you test long enough, you can prevent this kind of problem from making it to customers. Once the chip is verified to work at all, and it makes it through the infant mortality period, the lifetime is actually quite good. There are a few reasons: 1. there are no moving parts so traditional fatigue doesn't play a role 2. all "parts" (transisotrs) are encased in multiple layers of silicon dioxide so that you can lay the metal layers down 3. the whole silicon die is encased yet again in another package which protects the die from the atmosphere 4. even if it was exposed to the atmosphere, and the raw silicon oxidized, it would make silicon dioxide, which is a protective insulator 5. there is a degradation curve for the transistors, but the manufacturers generally don't push up against the limits too hard because it's fairly easy and cheap to underclock and the customer doesn't really know what they're missing 6. since most people don't stress their computers too egregiously this merely slows down the slide down the degradation curve as it's largely governed by temperature, and temperature is generated by a) higher voltage required for higher clock speed and b) more utilization of the CPU Once you add all these up you're left with a system that's very, very robust. The failure rates are serious but only measured over decades. If you tried to keep a thousand modern CPUs running very hot for decades you'd be sorely disappointed in the failure rate. But for the few years that people use a computer and the relative low load that they place on them (as personal computers) they never have a big enough sample space to see failures. Hard drives and RAM fail far sooner, at least until SSDs start to mature.