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I stopped trusting USB-C cable labels and started testing them

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Re: I stopped trusting USB-C cable labels and started testing them

#51

Post by pmarreck »

HDBaseT wrote: post #36
safeimp wrote: post #11

Verge recently posted this (free) app for testing on Mac's: https://www.theverge.com/gadgets/963759/whatcable-usb-c-cabl...

This effectively only tells you what the E-Marker reports though, the actual capabilities of the cable are still unknown. You can say the cable can do whatever you want on the E-Marker, its not the source of truth. The problem is, to actually benchmark everything, voltage drop, resistance, actual bandwidth (especially at Thunderbolt 5 speeds) requires a lot of hardware. Using a USB-C Test Controller ($13,000), connec…

well, that's disappointing; someone needs to miniaturize that and reduce the cost massively

Re: I stopped trusting USB-C cable labels and started testing them

#52

Post by Gigachad »

kiwijamo wrote: post #20

Interestingly, I have found a very mixed bag of USB-C cables I've collected over the years to generally just work for all my use cases. I can charge my various USB-C laptops at 65W with all the USB-C cables I have on hand. Maybe it's just my habit of just buying cables from known brands (Belkin is normally my go to) but I also have random cables that came with various devices of varying quality and all these also wor…

It’s because you are using the lowest use case for usb (like most people). Literally everything can manage 65w power only.

All of these “usb sucks” posts are about using multiple 4k 120hz monitors dasychained while pumping 140w and a handful of other dongles hanging off which pushes usb to the limit and requires carefully selecting the highest quality cables.

Re: I stopped trusting USB-C cable labels and started testing them

#53

Post by pmarreck »

rzzzt wrote: post #27
pmarreck wrote: post #23

The whole space is so scammy that I'd pay for a good USB-C cable tester

But how can we know which tester is good and which one is scammy?

I like your "who watches the watchers" reference, but AI's reviewing AI work, and notably, people reviewing people work, are subject to the same problem!

The same principles that worked for auditors tracking risk compliance in the 2000's now work for humans tracking AI-output risk compliance in 2026

Re: I stopped trusting USB-C cable labels and started testing them

#54

Post by Gigachad »

ChrisMarshallNY wrote: post #18

As always, these testers (the affordable ones) are capable of testing continuity, and, I guess, the cable chip report. If you want to test bandwidth, that's a five- or six-figure bit of gear.

It’s much cheaper to just buy your cables from Apple or LTT knowing they tested them on a 6 figure testing rig.

I throw out every usb cable that comes bundled with devices because they are literal junk.

Re: I stopped trusting USB-C cable labels and started testing them

#55

Post by Casteil »

joshstrange wrote: post #4
pogue wrote: post #3

Is there a cheap, reliable tester that someone can recommend that will test multiple USB cable types (A, micro & C)?

$45 https://www.amazon.com/dp/B0DYJL5Z67 This is the one I use and I quite like it. I've had it for a little over a year and a half. I used it to sort (or trash) all my cables and to test new incoming cables.

I just got this one a few days ago so it's kinda weird I've seen it mentioned or posted about multiple times since. Guerrilla marketing?

Anyway, it's definitely better than having nothing, and tests resistance as well. I tossed a couple low value/duplicate/high resistance cables because I've got too many just lying around causing clutter. Also helped 'confirm' my good (e.g. TB4+) cables that weren't labeled clearly are indeed good cables - granted, this is only as dependable as the marker chip the manufacturer added.

Re: I stopped trusting USB-C cable labels and started testing them

#56

Post by maya335 »

nerdsniper wrote: post #46
ChrisMarshallNY wrote: post #18

As always, these testers (the affordable ones) are capable of testing continuity, and, I guess, the cable chip report. If you want to test bandwidth, that's a five- or six-figure bit of gear.

This keeps needing to be pointed out every thread this appears on. Plenty of cables have eMarkers that claim "40Gbps" or whatever speeds, or support 240W PD...but absolutely cannot deliver either of those. And none of these consumer level testers can test either of those claims. Resistance measurements can cursorily test claims of 240W but resistance changes with temperature which changes with current...so unless you…

Yeah — "the eMarker said 40Gbps" is basically the same problem as trusting the print on the jacket.

For home use I've ended up treating real capability as an empirical property of the specific cable+port+device combo: does this exact cable drive this monitor at the mode I want, under load, for an hour? If yes, it gets a colored heat-shrink band and never leaves that use case. Everything else is a phone/charge cable until proven otherwise.

Re: I stopped trusting USB-C cable labels and started testing them

#57

Post by kimjune01 »

rzzzt wrote: post #27
pmarreck wrote: post #23

The whole space is so scammy that I'd pay for a good USB-C cable tester

But how can we know which tester is good and which one is scammy?

for throughput, you can use a stopwatch and a big movie transfer from one end to another

Re: I stopped trusting USB-C cable labels and started testing them

#59

Post by denkmoon »

retatop wrote: post #47
ssl-3 wrote: post #37

Earlier quoted context omitted.

Every not-broken USB C cable allows for 480Mbps USB 2 speeds and 60W charging. In USB C terms, it doesn't get any more basic than this; that's as low-and-slow the specification tolerates. The issues come into play with going beyond that. USB 3 speeds? USB 4? Thunderbolt? DisplayPort (4k uncompressed video!) alt modes? 240W charging? These are all practical things that regular people use USB C cables for every day, bu…

Not that I disagree with you, but I _wish_ "regular people" used 240W charging every day. As far as I can tell it's still pretty niche and hard to get 240W chargers

What device would I encounter in my day to day which would use 240W charging though?
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