The Framework is the most exciting laptop I've used

Re:The Framework is the most exciting laptop I've used by kragen on Tuesday September 21, 2021 @07:22PM (#28611257)

USB-PD permits 100 W with 20 V at 5 A. If that's carried over just two round copper wires (I don't know whether it is in USB-C) they would need to be 18-gauge or thicker for safety—about 0.94 millimeters. If they're copper, that's about 7.3 grams of copper per meter, 14.6 grams including the return path. Copper is expensive: almost US$7/kg. So a 3-meter 5-amp DC or two-phase cable would weigh 45 grams and contain 15¢ worth of copper. You could drop both the cost and the weight by going to aluminum. If you were designing the system from scratch, you could use 3-phase AC to cut the weight by half again, and use 48 volts to cut the weight by another 58%.

I don't have any idea how thick the 19 wires have to be for USB 40Gbps (GBps?) but I imagine the answer is "not nearly that thick".

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Re:The Framework is the most exciting laptop I've used by zepolen on Wednesday September 22, 2021 @02:06AM (#28613517)

Cables cost about 5$, no one would give a fuck if they cost $5.15

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Re:The Framework is the most exciting laptop I've used by Nextgrid on Wednesday September 22, 2021 @11:03AM (#28617121)

Bottom of the barrel vendors will absolutely give a fuck and will cheap out without telling you.

The advantage of USB 2 is that it's so simple that it's very hard to screw it up. You pretty much have to intentionally do it if you want to create a dangerous cable. Even the shittiest cable will work with the vast majority of devices (it might slightly heat up, voltage may sag at the receiving end meaning it will charge slower, but it'll somewhat work).

USB-C is significantly more complex and requires active electronics in the cable itself in some cases, and the potential for higher voltages means a faulty/recklessly-designed cable could request higher voltage from the charger and blow up whatever's connected at the other end.

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Re:The Framework is the most exciting laptop I've used by Dylan16807 on Thursday September 23, 2021 @01:10AM (#28625389)

The chip in the cable just identifies it. Cables don't request voltages.

And the cheap cables won't have that chip, so they'll support 60 watts.

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Re:The Framework is the most exciting laptop I've used by kragen on Wednesday September 22, 2021 @02:15AM (#28613561)

That's my thinking, yes.

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Re:The Framework is the most exciting laptop I've used by ethbr0 on Tuesday September 21, 2021 @09:31PM (#28612188)

Afaik, signaling frequency is typically cross-talk limited, vs diameter limited. Think more shielding, stricter tolerances over thicker.

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Re:The Framework is the most exciting laptop I've used by kragen on Tuesday September 21, 2021 @11:54PM (#28612968)

It sounds like you could maybe make substantial progress by just separating the differential pairs (?) by a millimeter or two of dielectric, giving you a ribbon cable, with much lower crosstalk than the round kind. Bonus points if you color the dielectric rainbow colors.

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Re:The Framework is the most exciting laptop I've used by Dylan16807 on Wednesday September 22, 2021 @05:28AM (#28614491)

I feel like it's harder than shielding and tolerances, given that longer passive cables don't seem to exist despite the very high prices people are paying for active cables.

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Re:The Framework is the most exciting laptop I've used by kragen on Wednesday September 22, 2021 @05:38AM (#28614539)

There might be issues of attenuation; we're talking about signals in the GHz range, where you have to use waveguides instead of wires to get low losses.

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