differential cable (capstan) drives aren't new.
if you think 1x Neo is impressive, check out the WAM arm from 15 years ago.
highly backdrivable, 0 backlash, super efficient (only rolling joint contacts), and capable of insanely low bandwidth direct joint-torque control.
it's also worth noting that this wasn't a research project, the WAM was in production. you could buy one for around $120,000.
so why didn't WAM dominate? In short, cables are a maintenance nightmare.
1x seem to know this and feel confident they've solved it.
in his S3 interview, the 1x CEO mentions that "like for us... [people say] 'oh you can't use tendons to drive a robot. They don't have reliability, durability and all these things. That's been tried many times before'... and then you try again, and try again for years, and you finally make it work".
btw Elon has said the latest gen Optimus hand is "tendon" driven too.
if you want to learn more about cables and their use in robotics, follow along below.
I'll go into technical details about cable drives, WAM arm and how 1x / Tesla could approach it differently: