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Comment by Retr0id | Hacker News Reader

For anyone else wondering, the "1000000x faster" claim is based on a theoretical clock speed upper bound of 1PHz https://newatlas.com/electronics/absolute-quantum-speed-limi...

> The team says that other technological hurdles would arise long before optoelectronic devices reach the realm of PHz.

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Not only, that, modern CPUs have transistors that switch in 0.1 ns. So even if they got to that speed, it would be 100,000x, not 1,000,000x.

And, if they only got to switching in 10 femtoseconds, it would be 10,000x, not 1,000,000x.

You might ask, what's two orders of magnitude between friends? But a job that takes a minute is quite a lot different from one that takes going on two hours.

Even 0.1ns is way slow. A modern silicon cmos gate will switch under 10ps, which is how we can fit 25+ gates in a single cycle at >3GHz. Everyone should remember that cpu frequency is not the same as the frequency a single gate can switch. Also keep in mind we are mostly wire limited anyway, as resistivity of copper at <50nm line widths is quite unlike its bulk resistivity, and scales super-linearly. This prevents us from further shrinking wires at all.

> resistivity of copper

Could we use a superconductor here instead of copper in order to achieve further wire shrinkage? Eg, if it were to be operated in a datacentre where it's plausible to power the cooler needed to keep it cold. The amount of superconducting material would be quite small

Microfabrication is quite an art. Being able to image pieces of copper down to such ludicrously small sizes with techniques like EUV and optical proximity correction is already quite advanced. Doing it for high temperature superconductors like YBCO is definitely not trivial. I don't think superconductors are a good idea due to the reduced fidelity, you might as well just use normal conductors and spread them out for better cooling

What about silver instead of copper?

Silver’s electromigration is significantly worse than copper, leading to reduced reliability. Plus the fact that silver is ~200x more expensive doesn’t help.

> But a job that takes a minute is quite a lot different from one that takes going on two hours

Though in your terms the promise would be to have a job that takes going on two hours in a second. Feasibility not discussed, one would not cry over those two orders of magnitude "that could not make it".

You can multiplex optical signals, though im not sure exactly how that would be harnessed. If nothing else, at least a few times more possible throughput?

You can multiplex electrical signals too. This is how some cable companies provided both TV and internet in the past.

> > The team says that other technological hurdles would arise long before optoelectronic devices reach the realm of PHz.

Yup... just the memory access (even if "instant", ram is so "far away" (physically) that the transmission delay will be many multiples of the clock... Currently this is a pain to implement correctly by the CPU manufacturers, but atleast with caches you don't run out of data to calculate while waiting for something new from RAM.

You can read the paper here: https://www.nature.com/articles/s41467-022-29252-1

I can see this technology being made into a super computer type setup one day, but as far as home computing, I have my doubts.

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