4 ms·

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

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 https://en.wikipedia.org/wiki/Pulse-amplitude_modulation

pclmulqdq 4y ago
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.
- Dylan16807 4y ago
  > 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.
  - segfaultbuserr 4y ago
    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.
    - aetherspawn 4y ago
      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.
      - Dylan16807 4y ago
        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.
jiggawatts 4y ago
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…
sophacles 4y ago
> 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.
- rektide 4y ago
  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.
  - sophacles 4y ago
    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)
tenebrisalietum 4y ago
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.

pclmulqdq 4y ago

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.

Dylan16807 4y ago
> 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.
- segfaultbuserr 4y ago
  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.
  - aetherspawn 4y ago
    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.
    - Dylan16807 4y ago
      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.

jiggawatts 4y ago

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…

sophacles 4y ago

> 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.

rektide 4y ago
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.
- sophacles 4y ago
  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)

tenebrisalietum 4y ago

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.