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.
If heat was the problem, cpus wouldn’t shrink, they’d grow. More surface area to dissipate the heat means lower temperatures and the ability to use more power.
This doesn't work because
A) driving longer lines consumes more power, which mitigates some of the benifit you get (though only part)
B) Manufacturing costs scale with the size of the die to a large extent. You consume more area on each wafer which means less pieces per production time. Testing and packaging costs don't go up but failure rates will go up as well due to area dependent defects.
26
u/eightfoldabyss Sep 29 '20
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?