I’m not a CPU specialist, but I took a course on CPU design at university a long time ago. Disclaimer: What I say may be wrong, either because I remember it incorrectly or because it has been simplified to the point that it is not factually true.

What I remember from those lessons is that the speed at which your signal propagates through a semiconductor depends on the voltage. If you want the speed to be higher, you have to increase the voltage. This increases heat, so you are limited in how quickly you can increase that speed.

Now of course you are thinking “what do you mean by increased speed, isn’t that 0.6x the speed of light?”. And this is correct: this is the speed of the current through the copper, and it is constant (at normal temperature). But we’re talking about the speed at which the signal propagates, and that’s a different thing.

If you have a 1 meter long cable with no voltage, then there will be 0 volts on it, so let’s call this signal 0. Now you take a 9 volt battery, and you apply voltage to it, and we agree that the signal is 1. To simplify everything, we agree that if Voltage below 4.5 volts, we read this as signal 0, and everything above is signal 1. This is very useful, because if your battery is not supplying exactly 9 volts, or if there is interference in the area that causes the voltage to fluctuate, then the signal remains Yours shows up as 1 or 0. I stand on the other side of the cable and read the voltage to see if you get a 1 or 0. It sends.

If you now connect the battery on your side, you can send signal 1 to the other side. After coupling, the electrons in the copper wire will continue to move at 0.6x the speed of light. That is, since the length of the wire is 1 meter, I will see the effect of your action after 1/200000000 second, or after 5 nanoseconds.

BUT: The effect of this is not that the voltage immediately goes from 0V to 9V! After 5 ns the voltage will start to rise. After those 5 ns, it will take some time before the voltage rises above 4.5 volts, and only then can I interpret your signal 1. I don’t remember how you mean how long it will take, it’s been a long time since the university was there for that

The same applies to the opposite: when you disconnect the battery, the voltage will start to drop only after 5 nanoseconds, and it will take some time before the voltage drops below 4.5 volts, thus reading 0.

Do you want your stress to rise faster? Then you can use an 18V battery. Do you want your stress to go down faster? Then you can use negative voltage.

This is why overclockers increase the voltage: the signal must propagate faster if you want to increase your clock speed. For the same reason, a lack of sense can make your system unstable: the signal propagates more slowly, and if it becomes so slow that it takes longer than a single clock cycle, you will get errors.

[Reactie gewijzigd door kiang op 23 oktober 2023 00:12]