Comment by rektide | Hacker News Reader

Comment by rektide | Hacker News Reader

Does anything else use PAM3? PAM4 is all over the place (PCIe 6.0 from this winter, 25/100/200 Gbe, GDDR6X, I forget who else but more), but PAM3... apparently once was used for 100BASE-T4[1]. That's 100 mbit, not Gbit, not 1000Mbit, 100 mbit.

Just so excellent that the USB4 nee-Thunderbolt tunneled/packet-switched architecture means that, if we do get a speed bump, that boost is a win for displays, storage, egpus connected via displayport, thunderbolt, what-have-you. (Not necessarily for those devices, but the % of throughput they consume diminishes respectively). The leap to USB4 is a huge shift, but tunneling/packet-switching has so many downstream benefits.

I'm sure to be downvoted, but- grasping the third rail here: does anyone else tire of every time USB being mentioned, the thread turning into a mudslinging festival? I find repetitive, almost never constructive, usually incredibly poorly defined (my dock didn't work-- ok, how? at all? doubtful) complaints repeated ad-nauseam, and there's such limited energy to refute the waves of negativity from the sore & aggrieved. I want there to be room for these voices, but the mere mention of USB is a magnet for misery. I can & apparently should write some blog posts on why things are they way they are, how incremental evolution happens, and how progress isn't always smooth. But to the larger phenomenon of muck raking being the popular activity at every mention: it's definitely not just USB, in online communities this vocal persistent complaint about topics is a social condition that, so far, has no remedy, no redress. Systemd had to deal with this, Kubernetes, react, rails; so many have had their time on the planet of being targetted subjects. It just happens again and again and again, and the world doesn't deserve to have only the negative so amplified. It'd be so nice to redirect these energies to more focused gathering places, and to let the actual news & events be discussed in peace.

To add a usb naming joke, and to build constructively & consistently on the past, this would obviously be USB4 2x12. Two channels of of 60 Gbps (5Gbps * 12). The previous USB4 2.0 would be 2x8. There, I fixed it for you.

[1] https://en.wikipedia.org/wiki/Pulse-amplitude_modulation

> I'm sure to be downvoted, but- grasping the third rail here: does anyone else tire of every time USB being mentioned, the thread turning into a mudslinging festival?

No. I was sold on USB being one cable to replace them all. Now we're back to making sure we carry all the right cables for our devices. The glorious 20 days of "all my accessories can be dealt with by one cable" was amazing and the USB folks decided to go ahead and screw that up.

to me it's exactly the opposite. but i've spent effort growing into this.

i carry a keyring of adapters, one good 1m $25 heavy-duty USB4 cable for connecting fancy stuff, & a regular short-ish light $8 usb3 100w cable for most daily usage. there are usb-c to anything pigtails/adapters up the wazoo: usb-a male/female, usb-mini-b, usb-micro-b, displayport male, displayport female, hdmi male, hdmi female, 20v dc barrel jack, 12v dc barrel jack. most are under $10, less than the specific cable. and a female/female c couplers for good luck/desperate times.

there's some subtle side-perks over dedicated cables to. the displayport & hdmi adapters often have power in, which means if the target is closer to power, i can run a ~2m usb-pd cable (if available) from power to target, & it shares the same extra 1m to laptop reach.

that i can carry a 100w battery that works with nearly any device is just chef kiss icing-on-the-cake/intensely better than where we were. thanks usb-c / usb-pd.

it sounds stupid, having a keyring of adapters. but i used to carry cables for everything, way too often/just-in-case. now i just carry one good cable, and a variety of jacks i can put on the end of it. it's a world of improvement to me. i'm not sure what world you lived in where one cable did it all- i always had display, power, data cables, and i also totally get how most people haven't realized how to properly/easily do usb-c with pigtails/adapter jacks, but wow, it's just night & day better to me, & i think it should be for you too.

Given the world that exists, I'm interested in this good cable and the adapters. Previous experience has shown adapters to be janky at best, but that could just be an area where tech has improved or I don't know how to find quality yet - what do you recommend?

(I reserve the right to still be salty over the wasted ideal of one cable to rule them all though)

I buy no name adapters & not a one has ever shown any issue for me. "ChenYang" USB-C female to displayport adapter? Runs my 1440p170 & 4k75 monitors fine. $15. Ditto for the literally no-name similar looking displayport adapter.

Your solution is useless for all but the 10% most tech literate users. And also involves carrying around a veritable toolkit of adapters and multiple cables.

It's not well understood/accessible. Yes.

But it's still far far more accessible with way less effort & burden than what came before. Functionality comes easier, cheaper, with less weight & more functionality. It is a new domain of knoweldge & understanding than the old ways buts it's better, easier, lower cost & more accessible.

The obviousness speaks for itself & re-defines the antiquated literacy of before.

Eventually the adapters ought go away. Beacuse every peripheral ought, if they give any cares, have a usb-c port. You can do whatever else might help. But do the good thing: have a usb-c lort that works on you device. You should. You should free us from legacy adapters.

Most people don't do high speed anything. I have a camera I can download video from but only at MicroSD speeds.

90% of USB cables are for charging stuff, or low speed things like keyboards. For an average person it's already close to perfect. Even PD over 30W is somewhat rare.

USB monitors will be a little confusing but still better than bulky HDMI.

The Base-T Ethernet standards get very creative about their modulation levels. 1GBase-T (IIRC) uses PAM-5. Using non-standard PAM levels is a very weird thing to do, and it appears to only be useful for optimizing speeds on old (or cheap) cables.

However, PAM-4 did originally have problems with transitions between the extreme levels (00 to 11 and vice versa). There was academic discussion of line codes that could eliminate these, but it appears that this kind of technology has fallen by the wayside in favor of PAM-3 for USB.

> The Base-T Ethernet standards get very creative about their modulation levels.

Yeah, just look at 100BASE-TX. It also uses 3 signal levels, but in a repeating cycle and the incoming bits decide how long to linger on each voltage.

Fun fact: Both 100BASE-TX and 1000BASE-T have a symbol rate of 125MHz.

Also an Ethernet fun fact: with 100BASE-T1 and 1000BASE-T1, you can now get Fast and Gigabit Ethernet over a single twisted pair. It's primarily used for embedded and especially automotive applications to simplify wiring. Both use PAM-3.

Are you perhaps mistaking 1Gbps with 1Mbps (1000K Baud)? Automotive networks are extremely slow, and there’s virtually no need for them to be faster.

The industry standard is to just add more pairs if you really need it, so you see cars now with 15-20 individual pairs each running at 500K or 1000K.

But these transports are extremely reliable, and still work in most failure cases — even if you unplug a terminator, splice some long random aftermarket branch, or ground or short one side. And they don’t use small cables either, usually just 20 AWG unshielded twisted pair (not even in a shared jacket). There is not much need for shielding or differential matching on PCBs, it’s not that sensitive.

Some newer forms of automotive networking used here and there for a time, but OEMs keep trying them, ditching them, and returning to slow networking.

Top google results for "1000BASE-T1":

> The 1000BASE-T1 MediaConverter establishes one direct point-to-point conversion between automotive ECUs using 1000BASE-T1

> DP83TG720S-Q1 1000BASE-T1 Automotive Ethernet PHY DP83TG720 is pin-2-pin compatible to TI's. 100Base-T1 PHY enabling design scalability with single board for both speeds.

> 1000BASE-T1 from Standard to Series Production. Enabling Next Generation Scalable Architecture. Olaf Krieger (Volkswagen), Christopher Mash (Marvell).

I don't know what they want the bandwidth for, but it's a real thing.

-T1 matters. Thats an uncommon variant. Most base-t & what most people would assume Gbe base-t means is base-t4, four twisted pair (-T4), connected via 8 pin RJ45.

IEEE 802.3bp is I think when 1000base-t1 happened: 2018. Way way way after rj45's 1000base-t4.

> -T1 matters. Thats an uncommon variant.

> 2018

Well yeah! That's why it was introduced as a "fun fact" that you "can now get".

> Are you perhaps mistaking 1Gbps with 1Mbps (1000K Baud)? Automotive networks are extremely slow, and there’s virtually no need for them to be faster.

No, it's not a mistake.

Electronics is a large field, quite a few concepts can be niche and unfamiliar even to its practitioners, so please don't assume something is incorrect just because you personally have never heard about it. I recommend doing a quick search first before trying to refute anyone. Here are just two examples I've came across recently:

1. Someone asked a question about a "DC-link" capacitor. One experienced engineer replied and claimed it's nonsense, because DC cannot pass through a capacitor. But in fact, it's a standard term in the power inverter industry that refers to the capacitors between an AC/DC and DC/AC power stage.

2. An article about Ethernet "magnetics". A reader replied and claimed the term "magnetics" is nonsense because they've never heard of it, if it's a transformer, just call it a transformer! But in fact, it's a standard term in Ethernet hardware that refers to both the isolation transformer and the optional common-mode choke at an Ethernet port. To a lesser degree, it's also valid in the power supply industry as a collective term for the magnetic components like inductors, EMI chokes, and transformers.

> Automotive networks are extremely slow, and there’s virtually no need for them to be faster.

High-speed, Gbps-level digital link solutions for automotive applications are currently being heavily promoted by semiconductor companies, it started since a few years ago. This is something you can immediately know just by a casual browsing of their websites and take a look of their latest chips, like Analog, Maxim, or TI. I assume this interest first came from the demand side, by the OEMs. You don't just make these chips for nothing.

One major application is the transmission of HD videos in a car entertainment system.

> Some newer forms of automotive networking used here and there for a time, but OEMs keep trying them, ditching them, and returning to slow networking.

You may be correct. This can be another attempt at it, and may or may not be ultimately successful.

All the things you listed are industry-wide standards or frameworks where people are essentially forced to use them. I mean sure, not at gunpoint, but they’re inescapable in practice, especially at typical workplaces.

All of those things are also fairly opinionated and all-encompassing, trying to be all things for all people… and failing to be a good fit for many of them.

Hence the grumbling.

You’ll see similar conversations about government too for the same reasons: forced on people, wide scope, poor fit for many.

Inevitably someone will say: “But you have a choice! You don’t have to use whatever the subject is!”

Sure… I can live on an island away from everything.

I’m a Windows systems integrator and I’m learning Kubernetes now even though it’s a poor fit for Windows.

Why? Because it’s the “new hotness” and several vendors support it and clients demand it.

So I’m forced to deal with something I don’t really want to. Not to say that k8s is necessarily bad, just that it’s not nice to deal with in my scenario…

USB deserves it. It's almost as bad as SCSI, but least the 50 different connectors were differently shaped and I could buy one that matches and know what it would do beforehand. I can't do that with USB.

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