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0 pointsmentos10y ago0 comments

What fraction of the speed of light are electrons moving at in the most advanced silicon chip we have? Trying to understand how much speed is left on the table for us to pick up in serial processing?

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4 comments · 2 top-level

dogma113810y ago· 2 in thread

It's not that easy to define because were talking about semi-conductors after all;)

They don't move at a constant speed like say in a conductor (which isn't the case either because electric field causes resistance e.g. eddy currents, but lets say a super-conductor)

You have quite a few concepts with semiconductors primarily saturation velocity (which in most cases is the peak velocity, but not necessarily attained in actual operation) which is also affected by the drift velocity due to any electric fields in your components.

https://en.wikipedia.org/wiki/Saturation_velocity

Light speed in vacuum is 29979245800 cm/s Saturation velocity in Si based SC is 10000000 cm/s

So there's quite a bit of difference there ;)

mentosOP10y ago

So does this imply an opportunity to improve computing speed by 2997?

dogma113810y ago

No because the speed of the components with the current designs is still limited by the switching speed of the masking matrix. And in any case you will still need to transform photons back to electrons twice. The speed of electrons or EM wave propagation vs photons isn't a player in why photonic computing might be better. The ability to encode more data into the photons, a much more power efficient and inherently parallel design are.

Also because light has much more shorter wavelength than "electricity" electromagnetic waves in conductors (kilometers vs nano-meters) you can have a much higher throughput with light even if you use it to replace the carrier wires in electronics (which is what Intel is working on they want to keep electronic switching but make all carriers photonic).

https://en.wikipedia.org/wiki/Speed_of_electricity

benp8410y ago

Light moves 3*10^8 m/s in a vaccuum, which is 7.5cm per clock cycle of a 4GHz processor. The processor is about 2cm wide, so not much room for improvement I figure.

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