From a signal integrity standpoint, you really don't want both pins (i.e. SSRX1 and SSRX2) tied together.
A lot of USB3 routing is reducing stubs. When the signals are going as fast as they are in USB3, they're essentially a wave going down the line, and if there's a "stub" the wave will actually hit the end of the wire and reflect back, causing interference. Having one of the pins not connect to your processor would create a stub inherent in the design, which is probably a bad idea.
When you dig into the details of the signals of USB3+ electrically it's truly remarkable they're able to mass produce cheap consumer grade equipment to implement it.
To give you an idea, the lengths of USB3 traces in your board need to be matched, so you add wiggles to the shorter trace to make it ever so slightly longer. But those wiggles can't get too far from the opposing trace in the diff pair either because that changes the way the traces are coupled together. Also, if the layer above/below is not a solid ground plane, you will run into issues as the signal will propagate through the wire faster/slower depending on what's around it. This is so critical that you use "impedance controlled" PCBs that place a tight tolerance on the spacing of your layers so that you can be sure it doesn't change along the length of your trace. And, of course, you want to avoid sharp bends in your traces as those will act like a stub.
None of this is bad engineering on the part of the USB IF, just that if you want to send data over a USB cable reliably at 5gbits, or now 40gbits, you're really pushing the limits of modern electrical design.
> From a signal integrity standpoint, you really don't want both pins (i.e. SSRX1 and SSRX2) tied together.
> Having one of the pins not connect to your processor would create a stub inherent in the design, which is probably a bad idea.
I was more thinking that each wire for a lane has two pins, one on the top and one on the bottom, which are electrically connected. So e.g. SSRX1+ on the top would be connected to SSRX1+ on the bottom, SSRX1- on the top with SSRX1- on the bottom, same for SSRX2+, -, etc.
With the same wiring in the plug as well as in the socket, there wouldn't be any disconnected pins. The wire for e.g. SSRX1+ would split before the plug, then lead to two pins in the plug; the plug connects to two matching pins in the socket which merge back into a single wire.
So in that modified header one differential pair would occupy four pins, two in the top row and two in the mirrored bottom row.
This means the header would have 4 additional pins per row (so 8 in total) compared to what it has now.
But of course the splits and merges in the wire might cause interference as well.
The four additional pins are a nontrivial problem. The Type-C connector is already annoyingly large as is. The stubs others have talked about are a major problem; they're really hard to avoid. In fact, they're so hard to deal with, that a lot of effort in routing goes to keeping things in the right order on the board.
By that I mean that when you leave, say, your upstream device and run the traces to downstream, you need to have them come out in the same order: if you start with _P on the left and _N on the right, you want to end that way. A swapover is annoying at USB 2 480Mbps speeds and utterly awful at 20Gbps. (There is also a >50% chance that you miswired the thing and are wiring _P to _N, which increases to >99% if the routing came out naturally neat, but that's just Murphy's Law in action.) It's so difficult and awful to deal with this stuff that USB 3 took a page from Gigabit Ethernet and usually features transceivers that just figure it out: they know you have eight wires in four pairs between eight pins and they can work with that.
Once you have that feature, and transceivers definitely do, there is no point whatsoever in trying to make superfluous changes at the connector bit.
The splits and merges would definitely affect signal integrity. Signal integrity is one of those fields that can feel like dark voodoo magic. I know people who are signal integrity experts by trade.
Would the splits and merges definitely make the signal integrity worse to the point that it wouldn't work? Maybe not. But if you're designing a high speed cutting edge standard, you probably don't want to make decisions that limit the best signal integrity an implementer could achieve. Signal integrity is all about balancing the bad SI decisions you have to make because of some product goal or whatever with tighter tolerances elsewhere. The more "clean" the standard is, the more tolerance it has for the implementers.
The signal reflections from the stub can propagate all the way back to the source. This means you’d have to use two transmitters to avoid interference from those reflections.
If there’s only one wire in the cable, and one trace leading up to the socket, would there still be a stub? Have the sockets pins both tied to the same trace, and have the plug terminals both tie to the same wire.
This is all pretty standard electronics design these days. If you're interested to learn more, you can search for "differential signaling".
What it comes down to is that once your signal rate is high enough, the speed that electrons move becomes a concern. Matching the length of your traces ensures that a signal sent down two wires at the same time arrives at the same time.
That's the general idea anyway. This topic gets very complex the further down you go
The other commenters got it spot on for where you can learn more, but as to where I learned it, I decided I wanted to build a project with USB C running at 3.0 speeds and had to deep dive on the subject in order to make it work.
It was surprisingly hard to gather all of this information in one place and actually implement it given the resources on the internet a few years ago. Even then, there were still some board revisions that got it a bit wrong, one where I left out the decoupling capacitors I'd later learn were a critical detail, and one where I put all the wiggles clumped together at the middle of the shorter trace and so despite both signals arriving at the end at the correct time, they were out of phase for nearly the whole trace run and caused (presumably) cross talk between each other. But I did get it working in the end :)
I think people lament that you could previously have the flagship experience for a couple hundred dollars, but now the flagships have become much less reasonable price wise.
> I think people lament that you could previously have the flagship experience for a couple hundred dollars
I think you're right. I imagine a lot of people don't like the feeling that something faster exists outside of their budget.
Ironically, I suspect these people would be happier if the faster cards simply didn't exist and the GPU lineup topped out at something like a 3060. It's funny that people get angry that faster parts simply exist.
I once had a gym membership which included a sauna, and would often take some time in the sauna after a workout. It really just depends how you want to spend your time
If you're ever in San Francisco, Miami, or NYC, check out what Revel is doing. Electric mopeds that rent for $0.50/min! They're such an excellent way to get around and see the city (at least in San Francisco where I ride them)
I saw this talk, Stop Drawing Dead Fish by Brett Victor, a while back. While I don't think it's the tool you're looking for, he does a great job showing why we may want better tools than we have currently and what they might look like. https://vimeo.com/64895205/description
I'm in the automotive industry and the biggest fan of EVs in general. I was even home-building an EV before I moved to the city.
I think we still have a lot to figure out with our charging infrastructure, in cities where often it's hard just to park. I want an EV badly, but it'd be a constant struggle to keep it charged.
There's also an issue with car companies generally not making the cars I want anymore, though I understand this is a me problem. There's not a nice plug-in hybrid small convertible, even if I could charge it.
EVs have really large batteries nowadays which should make home charging feasible for most. The Tesla Model 3 has an EPA estimated mileage of 358 while the Nissan Leaf has estimated 149. If you mostly travel within city limits, I'd be surprised if you could deplete your whole battery before you get home at the end of the day.
Indeed almost all EV charging happens at home, but the parent comment is talking about city living where people may not have access to charging at home.
Here's a video about this rootkit made by one of the Windows developers from that era. All of his videos are very entertaining and a unique look into Microsoft engineering from the 90s and early 00s.
An interesting thing about these trackpads, the hardware was actually pretty bad. It can only move the cursor in the X or the Y axis at any given time, i.e. the hardware does not support diagonal cursor movement.
Apple's driver did a great job of masking that with fuzzing and (I believe) predictive movement, that's the reason it seemed good in Mac OS X. But you can even tell in OS X if you're really looking for it!
"This is… you get to keep booth pieces" was the actual license text of something I ported to linux late in 1992 or early in 1993. (The middle bit was something about free software, I think.) Can't remember what software that was though.
A lot of USB3 routing is reducing stubs. When the signals are going as fast as they are in USB3, they're essentially a wave going down the line, and if there's a "stub" the wave will actually hit the end of the wire and reflect back, causing interference. Having one of the pins not connect to your processor would create a stub inherent in the design, which is probably a bad idea.
When you dig into the details of the signals of USB3+ electrically it's truly remarkable they're able to mass produce cheap consumer grade equipment to implement it.
To give you an idea, the lengths of USB3 traces in your board need to be matched, so you add wiggles to the shorter trace to make it ever so slightly longer. But those wiggles can't get too far from the opposing trace in the diff pair either because that changes the way the traces are coupled together. Also, if the layer above/below is not a solid ground plane, you will run into issues as the signal will propagate through the wire faster/slower depending on what's around it. This is so critical that you use "impedance controlled" PCBs that place a tight tolerance on the spacing of your layers so that you can be sure it doesn't change along the length of your trace. And, of course, you want to avoid sharp bends in your traces as those will act like a stub.
None of this is bad engineering on the part of the USB IF, just that if you want to send data over a USB cable reliably at 5gbits, or now 40gbits, you're really pushing the limits of modern electrical design.