3 ms·

Teeeeeeechnically I think yes, however in practice active cables are extremely rare (they start beyond 2m, not 50cm EDIT: incorrect, sorry!) and the redriver mi

Teeeeeeechnically I think yes, however in practice active cables are extremely rare (they start beyond 2m, not 50cm EDIT: incorrect, sorry!) and the redriver might even work for USB3 even if it's not specified. There isn't really all that much difference on the barebones electrical level; the most significant factor is the symbol rate, which is in the same range. (Not sure if the Type-C negotiation will prevent them from working; it might.) Ed.: after a quick check, active cables seem to crop up at 40G && >= 1m. 40G 2m cables seem to all be active, at 1m it's either. Couldn't find any "20G" active cables.

lxgr 6y ago
From what I've read, the redriver does break USB 3 connectivity [1], but it might also be the marker chip not explicitly indicating USB3 support. And I think the maximum length for passive Thunderbolt 3 40 Gbit/s cables is indeed 50cm [2]! 50-200cm would be 20 Gbit/s only; anything above always requires active cables. [1] https://appleinsider.com/articles/17/08/15/psa-thunderbolt-3-cables-longer-than-05m-generally-dont-support-usb-31-speeds https://appleinsider.com/articles/17/08/15/psa-thunderbolt-3... [2] https://blog.startech.com/post/thunderbolt-3-the-basics/ https://blog.startech.com/post/thunderbolt-3-the-basics/
- eqvinox 6y ago
  You're probably right, I can't check the TB spec but from what I see in shops I'm gonna say those "passive 1m 40G" cables are manufacturers breaking the spec. I'm also seeing "20G" cables that claim to only do 5G USB3, which is concerning & confusing me quite a bit... FWIW my confidence level on "would an active TB3 cable work for USB3 if it had the proper bits set" is somewhere along 66% to 75%; this is based on the SERDES in some (most?) TB3 host silicon being able to switch to USB3 to "downgrade" a port... meaning the electrical level can't be all that different... but I haven't dug into this.
  - eqvinox 6y ago
    While we're at it, I forgot the 2 SBU pins too, so that's 2 extra wires for TypeC-TypeC cables... neither USB nor TB uses them; native DisplayPort does (not including DP over TB) So, 15 wires in a full-feature C-C cable...

lxgr 6y ago

From what I've read, the redriver does break USB 3 connectivity [1], but it might also be the marker chip not explicitly indicating USB3 support. And I think the maximum length for passive Thunderbolt 3 40 Gbit/s cables is indeed 50cm [2]! 50-200cm would be 20 Gbit/s only; anything above always requires active cables. [1] https://appleinsider.com/articles/17/08/15/psa-thunderbolt-3-cables-longer-than-05m-generally-dont-support-usb-31-speeds https://appleinsider.com/articles/17/08/15/psa-thunderbolt-3... [2] https://blog.startech.com/post/thunderbolt-3-the-basics/ https://blog.startech.com/post/thunderbolt-3-the-basics/

eqvinox 6y ago
You're probably right, I can't check the TB spec but from what I see in shops I'm gonna say those "passive 1m 40G" cables are manufacturers breaking the spec. I'm also seeing "20G" cables that claim to only do 5G USB3, which is concerning & confusing me quite a bit... FWIW my confidence level on "would an active TB3 cable work for USB3 if it had the proper bits set" is somewhere along 66% to 75%; this is based on the SERDES in some (most?) TB3 host silicon being able to switch to USB3 to "downgrade" a port... meaning the electrical level can't be all that different... but I haven't dug into this.
- eqvinox 6y ago
  While we're at it, I forgot the 2 SBU pins too, so that's 2 extra wires for TypeC-TypeC cables... neither USB nor TB uses them; native DisplayPort does (not including DP over TB) So, 15 wires in a full-feature C-C cable...