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After 50 years of effort, researchers made silicon emit light

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Re: After 50 years of effort, researchers made silicon emit light

#91

Post by miscPerson »

jacquesm wrote: post #82
miscPerson wrote: post #79

Earlier quoted context omitted.

This is a tangent, but could you point me towards delay line + amplifier literature? Would be much appreciated.

That's how the very first computers worked: https://www.computerhistory.org/storageengine/edsac-computer... Not optical, but piezo electrical, usually with a crystal or air as the medium instead of mercury. Optical is much the same principle, a feedback loop incorporating the delay line, so the same bits get re-injected over and over again and can only be read out at specific points in time.

Yep, and I was looking for something applied.

Like most things, the concept is much simpler than making one work — and I was hoping I could find some papers on the applied side of photon delay lines. (Since OP commented it was related to his/her PhD.)

Re: After 50 years of effort, researchers made silicon emit light

#92

Post by Zenst »

datenwolf wrote: post #50

Gaaah, please stop advertising optical computers as the technology that will overcome Moore's law. It makes no effing sense. Wavelength of the light emitted by these devices: ~4000nm Latest generation commodity CPU transistor structure size: 7nm Add to that that photons really don't like being trapped; you essentially need a delay line and optical amplifier to hold them indefinitely (that's essentially the core techn…

How do electronics compare to photonics thermal radiation wise?

Though as always with electrical based electronics - superconductors are room temperature are always heralded to be the big jump in many things. As always, soon, much like photonics or let alone the ability to easily design and implement asynchronous circuits, let alone CPU's.

Though I do wonder what other industries have the equivalent to moore's law driving them in both advancements and marketing?

I'm kinda drawing a blank of anything that has any progress metric defined. Though hopefully somebody else knows of something comparable in another form of production/business.

Re: After 50 years of effort, researchers made silicon emit light

#93

Post by adwn »

jdsully wrote: post #75
adwn wrote: post #58

Earlier quoted context omitted.

> Secondly, could using a "photonic" memory bus bring RAM access speeds close to cache speeds [...] No, it really can't. The distance between CPU core and DRAM chips is approximately 10 cm, so at a typical electrical propagation speed of around 2/3 c, the round-trip time is 1 ns. A full DRAM access, however, is on the order of 100 ns. So physical transmission speed only accounts for about 1% of DRAM access times.

The speed is not limited by propagation delay, but by signal integrity. It is non trivial to have an external parallel bus operating at low Ghz speed. On chip signals can be much faster because they don’t have the capacitive load. On top of that is power requirements which are again orders of magnitude higher than on chip signals. Optical has a chance to fix that for the same reasons it works so well for longer dista…

What you're saying applies to throughput, not latency.

> On chip signals can be much faster because they don’t have the capacitive load.

You can routinely achieve > 30 Gb/s off-chip in copper cables over distances > 1 m using differential signaling [1]. Capacitive load is only a limiting factor if you directly drive the gate of a transistor.

[1] For example, high-end Xilinx FPGAs provide several of those transceivers. They really operate at > 30 GHz.

Re: After 50 years of effort, researchers made silicon emit light

#94

Post by jdsully »

adwn wrote: post #93
jdsully wrote: post #75

Earlier quoted context omitted.

The speed is not limited by propagation delay, but by signal integrity. It is non trivial to have an external parallel bus operating at low Ghz speed. On chip signals can be much faster because they don’t have the capacitive load. On top of that is power requirements which are again orders of magnitude higher than on chip signals. Optical has a chance to fix that for the same reasons it works so well for longer dista…

What you're saying applies to throughput , not latency . > On chip signals can be much faster because they don’t have the capacitive load. You can routinely achieve > 30 Gb/s off-chip in copper cables over distances > 1 m using differential signaling [1]. Capacitive load is only a limiting factor if you directly drive the gate of a transistor. [1] For example, high-end Xilinx FPGAs provide several of those transceive…

True it won't affect latency. Yet caches are pretty good at ensuring most DRAM requests take advantage of the hardware parallelization available.

That’s why despite DRAM having pretty much constant latency for the last 20 years bus speeds and bank counts have been consistently increasing. Optical interconnects will help immensely.

We may also see things like off chip SRAM come back into vogue once its feasible to take advantage of their performance.

Re: After 50 years of effort, researchers made silicon emit light

#95

Post by andrewflnr »

datenwolf wrote: post #50

Gaaah, please stop advertising optical computers as the technology that will overcome Moore's law. It makes no effing sense. Wavelength of the light emitted by these devices: ~4000nm Latest generation commodity CPU transistor structure size: 7nm Add to that that photons really don't like being trapped; you essentially need a delay line and optical amplifier to hold them indefinitely (that's essentially the core techn…

The article specifically proposes using light for transmission between components (not storage), with the efficiency benefit of multiplexing (albeit not mentioned by name). As I read it they're talking nanoscale fiber optics, not optical transistors and memory. This sounds pretty reasonable to me, and your comment seems to not address it at all.

Re: After 50 years of effort, researchers made silicon emit light

#97

Post by jl2718 »

datenwolf wrote: post #50

Gaaah, please stop advertising optical computers as the technology that will overcome Moore's law. It makes no effing sense. Wavelength of the light emitted by these devices: ~4000nm Latest generation commodity CPU transistor structure size: 7nm Add to that that photons really don't like being trapped; you essentially need a delay line and optical amplifier to hold them indefinitely (that's essentially the core techn…

High-bandwidth plasmon resonator waveguides. This would allow multiple datapaths on a single 'wire'. Fermions are great for logic and storage, but not for comms. Currently we use ~90% of chip power moving around data. We need to use bosons for this. We need to make them in silicon, and reduce the waveguide dimension. That's where this is going.

Re: After 50 years of effort, researchers made silicon emit light

#98

Post by jl2718 »

cs02rm0 wrote: post #12
knolax wrote: post #5

> Modern transistors, which function as a computer’s brain cells Who's the target audience for this analogy? If you understand what a brain cell is then you probably know what a transistor is too. I would bet that more people know what a transistor is than what a brain cell is.

I would bet that more people know what a transistor is than what a brain cell is. No chance. Everyone knows what a brain cell is, to some extent. Even people who have too few to rub together don't really feel like they know what a transistor is after reading the Wikipedia page for them, twice...

I used to know what a transistor was. And then we shrunk them to the point where they are no longer the same thing and yet they are still a thing, so I don't know what they are anymore.

Re: After 50 years of effort, researchers made silicon emit light

#99

Post by knolax »

capableweb wrote: post #8
knolax wrote: post #5

> Modern transistors, which function as a computer’s brain cells Who's the target audience for this analogy? If you understand what a brain cell is then you probably know what a transistor is too. I would bet that more people know what a transistor is than what a brain cell is.

You don't need to know the details of a brain cell to get the analogy. If I say "transistor" to my mom, she wouldn't be able to tell me what it is. If I say "It's like the brain cells for the computer", she would probably understand that "Ah, so a computer has many transistors that helps it think", which seems good enough for an article with a broad audience. > I would bet that more people know what a transistor is t…

But does your mother read Wired?

Re: After 50 years of effort, researchers made silicon emit light

#100

Post by kelsolaar »

datenwolf wrote: post #50

Gaaah, please stop advertising optical computers as the technology that will overcome Moore's law. It makes no effing sense. Wavelength of the light emitted by these devices: ~4000nm Latest generation commodity CPU transistor structure size: 7nm Add to that that photons really don't like being trapped; you essentially need a delay line and optical amplifier to hold them indefinitely (that's essentially the core techn…

I will be pedantic but there is no light at 4000nm. Light is by definition the radiation that is considered from the point of view of its ability to excite the human visual system (HVS). The HVS sensitivity, as given in ASTM E308-15 practise, is in range [360, 780]nm.
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