It would help if computers / phones had an easy way to just identify a cable when you plug it in. Is this hard to do or just something normal people never care about?
On the downside, it has highlighted what a cowboy industry manufacturing USB-C cables is.
Power capacity is relatively easy to measure ad-hoc via voltage drop from one end to the other...USB-PD controllers already do this and can even fine-tune the voltage to make sure that if the device receiving (sinking) power needs 20V they'll send 20.4V or 20.9V to compensate for voltage drop so that the charging device gets 20V on its end.
But actual maximum data throughput is hard to know. The only way to really "know" how much data can flow through a cable is with an expensive oscilloscope or cable tester. Because 80Gbps cables run at ~13GHz so, at minimum you need a 26GHz scope (Nyquist–Shannon sampling theorem) or more practically a 52GHz scope. And it turns out it's really expensive to measure electrical signals 52 billion times per second. The necessary devices start at $15,000 (cable signal integrity tester) [0] on the very low end and only work for max 10Gbps USB 3.2 cables, or past $270,000 for 80Gbps USB4 cables (proper 60GHz oscilloscope) [1].
On the high end, each signal integrity test device can actually cost $1-2 million [2] where the base unit starts at $670,000 plus then spending additional money for hardware-accelerated analysis, specialized active probes, and the specific PAM-3 / USB4 compliance software packages.
0: https://www.totalphase.com/products/advanced-cable-tester-v2...
1: https://www.edn.com/12-bit-oscilloscope-operates-up-to-65-gh...
2: https://www.eevblog.com/forum/testgear/uxr1104a-infiniium-ux...
If a USB4 device can output a USB4 stream and the receiver can check that stream for errors, isn’t that sufficient?
It could be reasonable for computers to be allowed to trigger a data throughput test and the peripheral would state "I support up to 40Gbps of receiving/sending", and then send a simple pattern that can be generated on the fly. But a lot of devices can't receive/send that 80Gbps of data for long enough to perform a decent test - the storage, RAM, buffers, etc get depleted or act as bottlenecks.
If you know enough to accurately interpret the measurements you get from that, you know enough to write your own computer program to try to send 80Gbps from one computer to another and use DMA to process it in real-time without hitting storage (which a lot of peripherals likely don't have the CPU to accomplish).
If you don't know enough to write those test applications, you probably don't know enough to interpret the results of a built-in test function and the measurements would confuse and frustrate a lot of well-meaning, nerdy, but under-educated consumers who make assumptions about why they're not actually getting the rated speed.
Idk, my opinion doesn't go one way or the other here. Perhaps I myself don't quite know enough to be a good judge of that concept.
All an end user cares about is if the cable is the bottleneck, if you think you have known-good devices. If I have a MacBook and a good NVMe enclosure, I want to know if my cable is fast enough, rather than have it quietly fall back to 3.2 or worse.
This is because the cross-sectional-area of the conductor would create an inflexible cable – and even then the connector (even though rated) could never handle a sustained 240W in the real world.
Fires. Fires everywhere... this is why no 240W chip exists.
src: electrician
USB-IF certifies plenty of USB cables as being tested safe for 240W. The reason 240W chargers don't exist is due to cost and a chicken-and-egg problem. There’s not really any demand for it.
Idealized, sure it'll work. But any realworld ports will be arc/fire hazards (e.g. after corrosion, wear, damage).
Just so I understand: would "extra snubbing" mean the USB-C cable wiggles less when plugged in (i.e. tighter tolerances)?
If so, this would probably mean it'll break/deform easier, too, no?
My above perspective is literally after decades of replacing burned-out devices (both freelance residential and IBEW datacenters), which "technically" are installed correctly — but know their realworld-alities.
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The concern I have is less about initial arcing (i.e. intentional [dis]connections), and more about long-term sustained powerdraw (I have seen soooooo many melted neutral terminals on 120V receptacles) on a loose connection. Connections become loose for a variety of reasons (including but not limited to bad installation), particularly on thermal throttlers (e.g. small wires, corrosion, cycling).
Does low voltage world have the same 80% derating as insidewireman-land (NEC/AHJ)? i.e. does a 240W PD USB-C allow continues 240W delivery (by protocol/standard/regulator), or is it neutered to 180W for "long-term loads" == 3+hr runtime (e.g. a computer display), with only ≥181W-peaking allowed..?
I just cannot see how such a small connector/cable can deliver sustained 240W, in the realworld that I've lived in.
Correct that this is only a worry about disconnects.
> The concern I have is less about initial arcing (i.e. intentional [dis]connections), and more about long-term sustained powerdraw
I think devices usually monitor voltage to make sure there isn't too much loss, and you're probably not going to get enough loose pins at the same time to see dramatic issues.
It's a valid concern, but it's a concern you'd see on almost any type of plug, isn't it?
> Does low voltage world have the same 80% derating as insidewireman-land (NEC/AHJ)? i.e. does a 240W PD USB-C allow continues 240W delivery (by protocol/standard/regulator), or is it neutered to 180W for "long-term loads" == 3+hr runtime (e.g. a computer display), with only ≥181W-peaking allowed..?
They're not worried about heating that takes more than 3 hours, so that specific kind of derating isn't part of the spec.
The 3 or 5 amp limit is designed around continuous load.
> I just cannot see how such a small connector/cable can deliver sustained 240W, in the realworld that I've lived in.
Well for sustained current we're worried about the amps, right? You get the same resistance and heat in the plug regardless of voltage.
Before USB C, we were putting 3 amps over a single pin each way in a USB Micro connector. Now with USB C we're putting 5 amps over 4 pins each way, with the new pins almost as big as the old pins.
nVidia_12VHPWR_sweating_bullets_.gif
(if unfamiliar, the 12VHPWR is the fire hazard found on some modern GPUs)
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In the trade-offs of amps verse volts, there are tradeoffs to be made. Yes, I agree that amperage is the primary generator of heat... but is voltage not the primary degenerator of insulations/gaps (particular one so user-interfacing). In a perfect world...
kids_phone_cord.frayed
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Thanks for the great discussion. I'm learning/adapting. This oaf breaks.things.lots
More voltage has more dangerous aspects, but 48 isn't all that high and in a steady state it's not causing problems.
For anybody unaware: a product has been built specifically to avoid a "rated" connector from melting down brand new perfectly installed GPUs.
[•] <https://www.tomshardware.com/pc-components/gpus/load-balanci...>
I'm envisioning some future frayedAF school laptop cord, where an increasing voltage correlates to higher likelihood that those amps can more-readily arc/jump (across melt, muck, and matter).
At the end of the day, an increase of either voltage and/or amps calls for a sturdier design (of ports and cables).
The cables themselves are already plenty tolerant from an insulation standpoint for 48V. Voltage is low enough to not harm anyone. The ports, as already mentioned elsewhere, are designed to have snubber circuits for rapid reduction in voltage during an unplug. There's a keep-alive to cut voltage as soon as it doesn't detect things plugged in anymore (or, perhaps, the cable gets damaged and can't communicate).
Seems to me like the sturdier design is already accounted for. I don't think "it's small therefore I don't like it" is a valid reason to distrust the standard inherently.
Thanks for writing this; it's where I fundamentally disagree, but appreciate your perspective. IMHO that's exactly the problem.
Your information is out of date. You can buy 240W chargers from Framework which I assume are just rebranded Delta chargers:
https://frame.work/products/power-adapter-240w
The Framework 16 supports this 240W charging input, as well.
The interface IC almost certainly also estimates signal quality, but it's likely hard to get that information out of it.
If only they all did. I have a significant percentage in my pile with no e-Marker chip. They'll be the first to be culled once I get around to that, mind.
This was on show hn only yesterday.
Probably can't tell you anything about the other end of the cable though.
> Is this hard to do or just something normal people never care about?
If i believed in conspiracies i'd say the usb consortium or mafia or whatever it's called is pressuring software developers to not display that info. Otherwise they'd have "normal people" with torches and pitchforks at their door.
There’s a reason that Windows barely shows any errors until the system fully halts.
The problem with most of those is that either users don't care until it's too late ("I need to get this done now, I'll delete files later"), third party applications are the cause and Windows can't/shouldn't interfere (did a program memory leak or is the user pushing the boundaries of what the system can handle?), or because there's not much the user can do about it ("your GPU driver crashed", well gee, my drivers are up to date, let me spend half a month's wages on a new GPU then, shall we?).
The only "too late" errors I've seen on Windows are when something very important has crashed and the system needs to shut down for data integrity (crss.exe crashing on school computers comes to mind, though I doubt that was the fault of Microsoft), or when something unpredictable went wrong, like a file ending up corrupt because of a failing hard drive or flipped bit in memory.
Microsoft actually created a dedicated screen to monitor errors and failures of all kinds (https://www.elevenforum.com/t/view-reliability-history-in-wi...) that's been around since Vista. It used to open up automatically if you clicked a popup after certain errors, but it appears Microsoft eventually stopped doing that. Going by how many "today I learned" posts I find when I look up the feature, I'm guessing nobody who actually understands what the screen does ever used the feature.
reality: kills dwm.exe (not the game that's the culprit and was running in borderless mode)
Given how DWM and video games both hit the GPU pretty hard, the death of DWM.exe can be anything from memory exhaustion to (GPU driver) bugs.