Comment by vel0city

> I'm a ham and took a number of EE/electromagnetism classes in college

Excellent! I had to learn all of this background the hard way by working with things in the field and asking myself why things behaved in certain ways. Finding answers that fit functionally into a larger mental model was not always very fast.

I should get a ham license one of these days. On a whim with no preparation, I recently managed to pass a technician-class practice test well-enough that a real test would not have been a problem. But I got tripped up badly on some of the questions about packet radio because many of the most-correct answers (in absolutes) were considered wrong (in the perspective of the older-timers who wrote that part of the test).

I mean, I know of plenty about TCP/IP. As my own brand of old-timer, I even know of KA9Q's work in packet radio and I think I even used his software ~35 years ago when running PPP under MS-DOS for dial-up internet, since that was the style at the time. I found that part that part pretty frustrating.

The rest of the practice test all made sense. :)

> I don't always have these things handy or ready to just plug something in quick and test.

Me, neither. I don't have any of this higher-speed stuff to play with at all. If I scored a great deal on some future-proof-ish all-singing, all-dancing USB cables, I'd have no way to validate their performance today. They'd be placed in a Rumsfeld bucket of known unknowns until something else changed, like the appearance of any kind of equipment to test with.

> I'd like some kind of small device which can actually do some quick tests and see if it passes or fails at whatever power and bitrate more than just what the little identifier says it can do.

Agreed. Perhaps it can be built. It's conceptually simple to say that the high-speed receiver and transmitter widgets exist as general-purpose COTS chips that can just get used in a circuit with some kind of supervisory intermediary to task them with Doing Verifiable Stuff Real Fast and provide performance information. Like UARTs, say.

But reality doesn't seem to match that very well at all. They instead seem to be very special-purpose ASICs that work in strictly-defined ways. This part is a motherboard/CPU glue chip (whooo boy), while this other part connects to a display (and only usefully-operates in display-world). None of them seem to be general purpose when I've looked into it.

And, of course: If it were easy then everyone would already be doing it. We'd just pick up some proper ludicrous-speed cable testers on AliExpress for fifty bucks or something. :)

(I guess we could tape out our own ICs, but I'm not prepared to visit that rabbit hole.)

> You'll potentially be clued in to it being closer to being a messed up signal, but not necessarily.

The point I was driving at with more-abstracted analyzers is that they can conceivably go beyond a pass/fail test.

Like: An edge-case cable that already presents a kind of smeary mess on the hypothetical Lambo-scope might actually work perfectly well, right now, in real use -- and I really do mean perfect. But is more likely to fail in noticeable ways after its performance degrades a bit and/or with less-tolerant electronics at either end. When every-day use requires it to work at 10/10ths, there's no room for things to get worse.

Meanwhile: A superior cable that presents a much clearer picture on the Lambo-scope might only be operating at, say, 7/10ths in every-day use. It has some room for its performance to degrade, or for less-tolerant electronics to be used, and still behave absolutely perfectly in the real world. This cable will tend to have better longevity and compatibility.

So above-and-beyond performance matters, I think. If I could make an informed choice between the edge-case cable or the superior cable for the thing I toss into my bag before a trip, I'm definitely not choosing the one that I know to be an edge case.

But without the moral equivalent of a Lambo-scope, I don't know how to characterize this or otherwise discriminate between these two cables' characteristics to that level of detail.

We don't have the technology to inexpensively do analytical work at these frequencies.

And this may ultimately be unsolvable: If we did have the tech, then some clever person would adopt it immediately to make an even faster data bus for the world to use and we'd be right back where we started, where the bus is faster than our ability to analyze it. :)