>"Even if signals in the chip were moving at the speed of light, a chip running above 5GHz wouldn't be able to transmit information from one side of the chip to the other".
That's almost completely misleading. Except for the clock itself, nothing that happens inside a processor takes a single clock cycle. And clock distribution delays need compensation anyway.
That's also true of memory. No one has ever seen 1-0-0-0 CAS RAM. (And no one ever will.)
It's true that pushing up against distribution times makes topology more complicated and lowers the maximum possible speed.
But that's actually the difference between electronics and photonics, which promise to run many orders of magnitude faster than EM-based silicon design. (I've seen "millions" quoted, but that may turn out to be hyperbole. Even so - optical fibre can run at tens of Tbps.)
Of course there's a difference between transmission speed, which is a function of the speed of light, and maximum data rate, which is a function of bandwidth.
But unlike electrons-in-silicon connections, photonics may not need to be 100% serial. It's entirely possible to get multiple data channels down a single line with frequency multiplexing, and perhaps also by phase rotation.
That has huge potential to change the packing density and the speed of processor designs; potentially you could have processor elements that were massively parallel but connected with single lines.
There's also some hope that because power dissipation shouldn't be such a problem, it will be easier to make 3D designs - although that's probably more speculative.
Bottom line is silicon is nearly done, but photonics is just getting started. Like fusion power it's probably a couple of decades away, but when it arrives it will be huge.
Most stuff that happens inside processors takes a single cycle, and we used to have single-cycle RAM until the CPUs ran away with increasing speed.
Photonics has a serious density problem: visible light is too large in terms of wavelength. This is already an issue with etching silicon. It's also at best at the 1950s stage where people have developed single photonic transistors in the lab but not yet photonic VLSI.
Anyway, the main factor of delay in chips is capacitance, both between wires and on the gates of FETs. This must be charged through the on resistance of the driving FET and all the intermediate wiring.
So, what you're really saying is that it's quite accurate, there are just details and more details but in the end - as long as we use a single clock - signals need to be able to travel from one end to the other in a single clock cycle.
Now, if we had (partially) clockless processors...
Also, your details are a lot more misleading than those in the article. lots of things in a modern processor take 1 clock cycle. Agner has lovely tables:www.agner.org/optimize/ and note that most basic integer and floating point operations on a skylake processor take 1 cycle - things like bit shuffling, moving, adding (not floats), and quite a few incidental other operations. Now, I'm sure you can quibble that a latency of 1 cycle in that table isn't really 1 cycle under some unusual interpretation of what's going on, but at that point you're quibbling about what "doing something" means, which isn't helpful. What programmers/compiler writers call 1 clock cycle can execute what most people call 1 instruction for many common instructions, even today.
On the massively-parallel-connected-with-single-lines theme, there's been some interesting work done with on-chip RF, which does essentially the same thing with conventional silicon.
That's almost completely misleading. Except for the clock itself, nothing that happens inside a processor takes a single clock cycle. And clock distribution delays need compensation anyway.
That's also true of memory. No one has ever seen 1-0-0-0 CAS RAM. (And no one ever will.)
It's true that pushing up against distribution times makes topology more complicated and lowers the maximum possible speed.
But that's actually the difference between electronics and photonics, which promise to run many orders of magnitude faster than EM-based silicon design. (I've seen "millions" quoted, but that may turn out to be hyperbole. Even so - optical fibre can run at tens of Tbps.)
Of course there's a difference between transmission speed, which is a function of the speed of light, and maximum data rate, which is a function of bandwidth.
But unlike electrons-in-silicon connections, photonics may not need to be 100% serial. It's entirely possible to get multiple data channels down a single line with frequency multiplexing, and perhaps also by phase rotation.
That has huge potential to change the packing density and the speed of processor designs; potentially you could have processor elements that were massively parallel but connected with single lines.
There's also some hope that because power dissipation shouldn't be such a problem, it will be easier to make 3D designs - although that's probably more speculative.
Bottom line is silicon is nearly done, but photonics is just getting started. Like fusion power it's probably a couple of decades away, but when it arrives it will be huge.