3 ms·
We have one HN member here very adept in matters of interconnect: @deepnotderp Saying from my IC design exposure really many years ago, those ultra fast, and u
by baybal2 5y ago
We have one HN member here very adept in matters of interconnect: @deepnotderp
Saying from my IC design exposure really many years ago, those ultra fast, and ultra complex short range serial signalling methods are also ultra power hungry.
Past the PAM4, signalling over copper hits a power consumption wall where you can no longer get more speed by throwing more transistors at it, because any speed gains from extra signalling complexity start to be offset by the need to reduce the transmitter clock frequency to keep it from melting.
I believe PAM4 will be the swan song of sophisticated serial signalling before the industry switches to optics.
The industry possibly have one last trump cards in the sleeve: chord signalling, which is currently being developed by Kandabus. It's an extremely complex signalling scheme, with analog signal equalisation, and other signal conditioning techniques bordering on black magic. Its design cost, and complexity may well be higher than going straight to optics.
- cyberge99 5y agoI believe Thunderbolt 4 has a fiber optic spec coming.
- somerandomqaguy 5y agoAs in fiber optic? Apologies for being ignorant, most my experience with with fiber has been with very small runs of OM3 and OM4 as trunks between network switches. But isn't fiber optic cable less tolerant of the kind of abuse that a short USB cable would see? Being throwing into someone's purse or having it repeatedly pulled by the cable or just being folded in half over and over again, stuffed in a pocket and sat on. Is fiber really suitable to replace the kind of short range interconnects USB handles?
- baybal2 5y ago> But isn't fiber optic cable less tolerant of the kind of abuse that a short USB cable would see? A USB 3, or TB cable will be dead long before a toughened single mode cable from an equivalent amount of abuse. I had many TB cables which degraded, or died completely simply from gently rolling, and unrolling them a few times. I had a single mode cable in the office being driver over by heavy carts, and stepped on for years without it giving in. Multimode cables though are way more prone to signal distortion from mechanical stress because of their their thicker cores.
- merb 5y agobtw. corning builds optical thunderbolt cables.
- somerandomqaguy 5y agoReally? Color me surprised. Just reading a bit more into it now, I always thought that it fiber optic was made of glass which was why optical cable was always more expensive and more delicate. Never heard of polymer based optical cables until now, and combined with a more robust sheathing... Would the total cost of cable then be somewhere in the same scale between an active circuit cable like USB 3.1 onwards vs a optical one with the laser transceivers and the like, assuming data signalling protocols?
- baybal2 5y agoThe optical cable itself is made of glass in a plastic sheath. It's very cheap because there are millions of kilometres of it used around the globe. And yes, the tiny few micron glass core is actually more tough than thicker copper cables. It's only sensitive to extreme, like 180° bends, and a thicker insulation will prevent permanent damage. The cheapest single mode SFP transmitters cost like 5-10 dollars wholesale. If they were manufactured in volumes comparable to USB chips, they would've probably cost close to one dollar.