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10GBASE-T uses four pairs full-duplex for 10 GBit/s total BW per direction. USB 3.0 uses one pair per direction for 5 GBit/s. The analog bandwidth of USB 3.0 ex
by formerly_proven 6y ago
10GBASE-T uses four pairs full-duplex for 10 GBit/s total BW per direction. USB 3.0 uses one pair per direction for 5 GBit/s. The analog bandwidth of USB 3.0 extends to 3+ GHz. 10GBASE-T only goes up to ~400 MHz or so.
Running at much lower frequencies makes it reach much farther, makes it more immune to EMI and makes it more reliable (because the margins are much fatter when you are only using 10 % of the possible minimum cable length).
- michaelt 6y agoHow is 10GBASE-T able to get so much data into 400 MHz, when USB 3 had to go to 3 GHz to achieve the same thing? Other than the fact 10GBASE-T buyers are ready to spend a lot more per port :)
- formerly_proven 6y agoUSB 3 is a pretty plain 8b10b scheme. 10GBASE-T uses a far more complex modulation scheme which uses forward error correction, then applies a PAM-16 modulation and then packs two PAM-16 symbols into a 2D constellation of 128 symbols called DSQ128 (curiously two PAM-16 symbols would encode 256 values, but DSQ128 only contains 128). Four pairs vs one pair already quarters the bandwidth requirements on top of that.
- vlovich123 6y agoIs there a reason that USB isn't adopting those techniques? Too much compute required? Four pair cabling is prohibitively more expensive in this niche?