4 ms·

CPU have error correction, which will mitigate transistor aging and make the CPU work slowly instead of not at all. It will not "perform the same". At some poi

• rcxdude 6y ago
  Error correction in CPUs is generally limited to the cache, and its incidence is recorded: if something had failed permanently such that the error correction path was being taken constantly, you would be able to record it. Absent a mechanism which reduces the clock speed of the CPU when it becomes unstable, there's no reasonable way in which failures in the CPU will result in it running slower. Such a mechanism doesn't generally exist: modern CPUs regulate their clock but only in response to a fixed power and temperature envelope. The recent iphone throttling is the only notable case where anything was done automatically in response to an unstable CPU, and that consisted of applying a tighter envelope if the system reset. This is reflected in the experiences of those who run older hardware with contemporary software: it generally still works just fine at the speed that it used to.
  • jokoon 6y ago
    From the article: > “For example, microprocessor degradation may lead to lower performance, necessitating a slowdown, but not necessary failures
    • rcxdude 6y ago
      It may be necessary for the micro to run slower in order to be stable, but to my knowledge no system for making that adjustment automatically exists in the vast majority of systems. The main problem being it's hard to detect. How do you tell if the CPU is on the margin of failing without a huge amount of extra circuitry? It can be hard enough to detect that it has had a fault. It's not due to lack of interest: such sensing approaches have been patented before, but don't seem to have made it out of the R&D lab.
      • jokoon 6y ago
        "to my knowledge" CPU technology is quite arcane, very high level, there are so many patents, IP money and a lot of secrecy involved, since CPU tech is quite a strategic one for geopolitical power. Do you work as an engineer at intel, ARM, AMD? On chip design? > How do you tell if the CPU is on the margin of failing It's not about failing, it's about error detection. Redundancy is a form of error detection. If several gates disagree on a result, they have to start again what they worked on. That's one simple form of error detection. CPU never really fail, they just slow down because gates generate more and more errors, requiring recalculation until they finally correct the detected error. An aged chip will just have more and more errors, that will slow it down. Which is the reason why old chip are slower, independently of software. Although a CPU that is very old will be very slow, or just crash the computer again and again that hardware-people will just toss the whole thing, since they're not really trained or taught to diagnose if it's the CPU, the RAM, the capacitors, the GPU, the motherboard, etc. In general they will tell their customers "it's not compatible with new software anymore". In the end, most CPUs get tossed out anyway. It's also a matter of planned obsolescence. Maintaining sales is vital, so having a product that a limited lifespan is important if manufacturers want to hold the market.
        • rcxdude 6y ago
          > CPU technology is quite arcane, very high level, there are so many patents, IP money and a lot of secrecy involved, since CPU tech is quite a strategic one for geopolitical power. Do you work as an engineer at intel, ARM, AMD? On chip design? If such a mechanism existing it would be documented at at least a high level and its effects observable under controlled tests. Neither are, in contrast to the power and temperature envelopes I mentioned. There is no actual evidence that aged chips operating with the same clockrate perform computation slower, your subjective experience that hardware 'slows down' does not count. > It's not about failing, it's about error detection. Redundancy is a form of error detection. If several gates disagree on a result, they have to start again what they worked on. That's one simple form of error detection. > CPU never really fail, they just slow down because gates generate more and more errors, requiring recalculation until they finally correct the detected error. An aged chip will just have more and more errors, that will slow it down. Which is the reason why old chip are slower, independently of software. This is not how consumer CPUs work. It's not even how high-reliability CPUs necessarily work (some work through a high level of redundancy but they don't generally automatically retry operations when a failure happens: that's a great way of getting stuck). Such redundancy is so incredibly expensive from a power and chip area point of view that no CPU vendor would be competetive in the market with a CPU which worked like you describe. If a single gate fails in a CPU, the effects can range from unnoticable to halt-and-catch-fire. The only error correction which is present is memory based, where errors are more common and ECC can be implemented relatively cheaply compared to error checking computations.
• thebruce87m 6y ago
  Someone else has addressed your other points, but for ECC: This will not detect an error in computation, only a bit flip in data. The current way to mitigate computation errors is to have two processors to detect an error in computation, or more to do a voting system if mere detection is not good enough. Since you cannot detect a computation error with a single CPU (without overhead somewhere, and thus lower performance), you can’t slow down to fix it. The ECC systems I have worked with can fix a 1 bit error and detect two or more bit errors. They do this by using an algorithm to convert the original data in to an output that is bigger than the original (e.g. 64 bytes is now 72 bytes). This output data does not make sense until passed through the reversing algorithm. So basically the overhead is zero since the memory controller is running the algorithm in hardware every time anyway, so no slow down.