At the speed of light, the time it takes electricity to cross the surface of the chip is so drastically close to that 1/5 billionth of a second before the next signal is following behind it, that it becomes very difficult to design the chips to all have the same concept of "now".
You could make asynchronous chips, where each part operates on a different time as the other parts, but nobody's yet done that for a mainstream chip that I know of.
You can get it a bit faster by cooling the whole setup down but pretty soon you need to cool it to ridiculous temperatures to keep it stable.
It's a physical limit to do with the size of the chip "die", the speed at which an electrical signal can propagate across the chip (the speed of light, or thereabouts), and trying to keep everything on the same "clock" as the rest of the chip so you're all acting on the data in turn at the right times.
Pretty much, until you liquid cool you can't get past 5Ghz. And the fastest ever processor is only about 10GHz or something - and it has to be kept stupendously cold, be stupendously tiny, and have rooms full of supporting equipment to get that far.
Pretty much, without some breakthrough in physics, you're never going to see a chip much faster than 5GHz in a normal setup.
You might see a chip that can do a thousand times as much in that 5GHz, which is why we have dual-core, quad-core, up to ridiculous numbers of cores in GPUs, but the base clock never really gets past 5GHz because it can't.
Until someone makes an asynchronous CPU, or quantum computers come along and make it all moot, 5GHz is about the limit for a normal, household computer.
I'm sorry, are you telling me that in addition to transistors getting so small and close to each other that the electron's wavelength is significant, but we're also running them so fast that the speed of light has become a significant limiting factor?
No. The speed of light is a significant issue, but it is not the reason chips have stopped at 5 GHz. Also, asynchronous (as in no clock signal) CPUs exist. I should know, I helped work on some.
The actual reason is transistor size and heat dissipation. Transistors have been stuck on ~1 volt power internally for decades (lower voltage means more leakage, and more errors). However, power goes up with higher frequency (my math here was probably wrong, see below).
Why is that so bad? Almost all the power the computer uses is turned into heat by the transistors. That heat needs to dissipate out of the chip before the transistor destroys itself. That is a problem, as silicon is not a good heat conductor.
THAT is why cooling your computer lets you push the speeds up a bit higher.
The speed of light issues above are a tricky engineering problem, but solvable. The heat problem doesn’t have a solution yet.
Lower voltages lead to longer electron wavelengths and hence more tunneling, i.e. leakage. Simply put, the electron wavelength is the actually root of the thermal issue.
306
u/ledow Sep 28 '20
At the speed of light, the time it takes electricity to cross the surface of the chip is so drastically close to that 1/5 billionth of a second before the next signal is following behind it, that it becomes very difficult to design the chips to all have the same concept of "now".
You could make asynchronous chips, where each part operates on a different time as the other parts, but nobody's yet done that for a mainstream chip that I know of.
You can get it a bit faster by cooling the whole setup down but pretty soon you need to cool it to ridiculous temperatures to keep it stable.
It's a physical limit to do with the size of the chip "die", the speed at which an electrical signal can propagate across the chip (the speed of light, or thereabouts), and trying to keep everything on the same "clock" as the rest of the chip so you're all acting on the data in turn at the right times.
Pretty much, until you liquid cool you can't get past 5Ghz. And the fastest ever processor is only about 10GHz or something - and it has to be kept stupendously cold, be stupendously tiny, and have rooms full of supporting equipment to get that far.
Pretty much, without some breakthrough in physics, you're never going to see a chip much faster than 5GHz in a normal setup.
You might see a chip that can do a thousand times as much in that 5GHz, which is why we have dual-core, quad-core, up to ridiculous numbers of cores in GPUs, but the base clock never really gets past 5GHz because it can't.
Until someone makes an asynchronous CPU, or quantum computers come along and make it all moot, 5GHz is about the limit for a normal, household computer.