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Optical PCIe 7.0 connection hits 128 GT/s

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204 points WithinReason | 2 comments | 17 Jun 24 11:42 UTC | HN request time: 0.423s | source
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yjftsjthsd-h ◴[18 Jun 24 00:02 UTC] No.40712649[source]▶
So I guess what this makes me wonder is: Why are we using electrical signals to connect the data lanes between components and computers these days, rather than moving everything to optical for data movement (obviously power would stay electrical, but that's already on separate lines)? I assume there's an element of cost, and once the photons get where they're going they have to be turned back into electrical signals to actually be used until such time as we get around to getting pure light based computers working (someday but not yet...), but that must not overwhelm the advantages or we wouldn't be looking at this being developed.
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1. ryukoposting ◴[18 Jun 24 13:49 UTC] No.40717847[source]▶
We're a lot closer to the limits of copper than I realized. Apparently motherboard designers have to make the length of clock/data traces for DDR5 memory as close to equal as possible, otherwise the entire bus just doesn't work right (maybe this isn't news to other folks).
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2. bangaladore ◴[18 Jun 24 14:10 UTC] No.40718082[source]▶
You have to do that for all high-speed multipin interfaces. Generally, once you get past roughly 100 MHZ, it is good practice to match the lengths as well as possible, even though it probably doesn't matter until a couple of gigahertz (it depends on many factors, but generally, signals move at 15 cm per nanosecond on PCBs).