I'm missing something. From what I've read, it should be technically possible to run two or even three monitors off the USB-C port in my Dell XPS 13, but I can't figure out how. There are plenty of devices that will add an HDMI port, but I can't find any that will add two.

Is this not possible? The best I've come up with is an adapter that'll do HDMI and VGA, and that's not acceptable as a desktop setup.

It doesn't have to be HDMI either. I'll DP, mini-DP, whatever can drive a good quality display. I also don't need it to support 4K at all.

I've seen some USB3 adapters, but I've had bad experiences with those. I tried to get one to work for a client a little ways back, and the driver support was a nightmare and the thing never really worked all that well.

Any ideas? I thought I read at one point that there were even plans to make devices that could daisy chain through USB-C, so that a monitor would have in/out ports. Did I dream that?

The USB3 monitor docking stations are a mixed bag, so I understand why you would have had trouble with one. Driver-wise, it's important to remember that they're all just DisplayLink adapters so I just go get whatever is the latest driver at the http://www.DisplayLink.com site. Anyay, I got this one a while back and was happy with it, though I'm sure there are even better ones now: https://www.amazon.com/gp/product/B006ZGWJU2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Note that it has an HDMI and a DVI plug, which you complained about specifically: I just had the necessary cables so that I could drive both my external monitors of of those two plugs directly (HDMI plug to DVI plug is just a cable with different endings, not a converter of any kind).

I don't know anything about USB-C monitor connections. I wonder if it's one of those things where, you just need a USB-C hub and some USB-C-capable monitors; i.e., direct-plug-USB monitors, as opposed to HDMI/DP/etc? Dunno.

DVI is fine for the reason you said. It was VGA that I was complaining about.

I'll think about it. I'm also interested in going through the USB-C port because of it's theoretical one-cable capability. Docking stations are a think of the past, it seems, and I have a lot of clients who would like to simply make one connection to their laptop and that's it. If I could make that one connection the USB-C port, which can already get power, then that would be a good replacement for those old bulky docks. So far, though, I'm at a loss for how to hook up more than one monitor using such a configuration...

Is it "plain" USB-C, or is it Thunderbolt 3 on a USB-C connector? If the latter, there's stuff like this: https://eucomtech.eu/uk/thunderbolt-3-to...CFakW0wodl4gBDA

Peter

Hmm, I'm pretty sure it's Thunderbolt, but I'll have to look that up. If that's the case, I could use that along with two Displayport to HDMI cables... Thanks!

The only problem is that I would still not achieve that "one cable" ideal, since there's no power or even other USB connections on that adapter...

Argh, I thought I was on to something. I just remembered that displayport can support daisy chaining, so I figured I'd look for a USB-C hub that had displayport in it...no dice. There are plenty of hubs with HDMI and adapters with displayport (only), but nothing with both. Argh.

*edit*

Ok, now I'm really wondering what's up. This Verge article from May describes a USBC hub with minidisplayport in it, but for some reason it only had USB2 not 3. Now the links to that company's website for that device are dead, and their site only lists a USBC hub without any monitor connections at all.

This is strange...

If your PC has Thunderbolt, stop looking for USB-C hubs and start looking for Thunderbolt hubs e.g. this one.

Peter

Is it the exact same connector? I thought it was different.

Also, I looked at that exact model, but it gets absolutely horrendous reviews due to very bad driver support from Dell. I wasn't even able to bring it up on Dell's own website so I'm not sure they make it anymore. It's sold through a 3rd party on Amazon. That's one of the things that made me start wondering if there's some sort of unreported problem with USB-C, that the only two docks I've seen with multiple monitor support have been removed from the market...

Surely you jest! This is the worst review percentage I have ever encountered on Amazon.com. Am I missing something here?

tanstaafl.


Gaahhh! You beat me by 10 measly seconds!

I have a XPS 13. Yes it supports Thunderbolt 3 over the USB-C connection. You can get a number of double display adapters (4K @ 60Hz x 2) but that's all they support. No power, USB, Ethernet etc. There are a number of adapters that do USB-C only and thus only have HDMI or VGA outputs. The main issue for me is the lack of 60Hz output. I've lived with 30Hz though and for desktop/programming it's really not that bad.

The Dell TB15 dock linked on Amazon was released early this year but had massive driver, stability etc problems. Even with driver, BIOS etc updates it was still dodgy. That's where all those bad Amazon reviews came from.

I noticed I got a Thunderbolt firmware update just recently for my XPS 13 so maybe that's fixed it finally? They had stopped selling the TB15 completely for a while. Perhaps it's "fixed" and back on the market? On paper it will do what Matt is looking for (and me too).

I was looking for a single plug in solution. Ethernet, 4k@60Hz DisplayPort output, some USB ports and USB-C power pass through. That way I could dock my laptop with one cable.

It has one really dumb design feature. The cable comes out on the left but the XPS 13 also has the USB-C port on the left. The cable is short too so it's quite awkward to place on the desk.

Looks like the TB15 is still not officially for sale from Dell. Their recall/stop ship is still in place.

Unfortunate as it seems to be the only device capable of what I want.

The only thing I can think of is to use one of the USB-C hubs with HDMI and USB, then for the second (and third, etc) monitor try using a USB to HDMI adapter. I have the sneaking suspicion that it wouldn't work very well, but it would be interesting to try.

The hub with built-in HDMI is simply a USB hub, plus a USB-to-HDMI adapter, plugged into said hub, all inside a uniform enclosure.

So if the "built-in" one works, then so should the external USB-to-HDMI adapter.

It's all DisplayLink stuff.

Is DisplayLink any different or improved for USB-C over and above USB-3?

DisplayLink is still DisplayLink running what is an basically external graphics card over USB (vs an internal one on PCIe).

However DisplayPort over USB-C/Thunderbolt 3 can use the internal graphics device and therefore isn't subject to bandwidth limitations of USB-C/Thunderbolt. That said 5/10/20 (USB-C) or 40 (Thunderbolt 3) Gbps should be plenty to run half decent graphics. Even USB 2.0 did a reasonable job for general coding/office type duties.

The bit I'm confused over is whether the USB-C/TB3 to DisplayPort adapter I have actually runs USB-C or Thunderbolt 3. I think it's only USB-C. Thunderbolt 3 allows 2 x 4k@60Hz displays.

Under Linux, "lsusb" should show all of the USB devices. If your display (adapter) is listed there, it's using USB protocols.

Ahhhh. Interesting. That kind of bites. It's not at all what I thought was happening. So basically I'm better off just buying a USB3 hub and plugging however many HDMI adapters I want into that? Along the lines of Tony's question, would there be a bigger performance hit if I did it that way versus that USB-C hub? I suppose the main advantage of the hub is that I get that "one cable" arrangement, and it's sounding more and more like USB adapters would be the way to go in that situation.

This is mostly a thought experiment for suggesting setups like these to my customers. For my own purposes, I'd probably get one of the monitors out there that use USB-C with power delivery. This LG, for example. This Acer seems like a more affordable option, if I can stand the gold color.

My understanding, possibly incorrect, is that "USB-C" is merely a connector type for USB2/USB3/USB3.1. The other end of the cable can also have a USB-C connector, or a USB-A connector, with no difference in electrical functionality.

So a "USB-C" hub, is merely a USB3 (or USB3.1) hub, that happens to have USB-C connectors rather than USB-A connectors. Nothing magic about it.

As discussed above, some USB-C host connector implementations also support an "alternate mode" electrical interface, eg. "Thunderbolt" which seems to be a type of PCI Express interface merged with a DisplayPort interface.

But doesn't USB-C have more throughput? Isn't there something different about it? Is it going over that same bus as the other USB ports?

Nothing magical. Just a connector. My Nexus 5X has a USB-C connector on its USB 2.0 port.. 480mb/sec max, same speeds as one would expect from any other type of USB 2.0 port.

Ditto when a USB 3.0 system has a USB-C connector: still "only" 5gb/sec max.

Now.. the new notebooks that sport USB-C ports, generally implement USB 3.1, which is faster: 10gb/sec. But they could do that with a USB Type-A port just as well, though clunkier.

Cheers

USB-C ports/cables have a few advantages I can see:

1) Reversible non-polarized mechanical plug. Easier to use.
2) Smaller size.
3) Spec'd for carrying higher electrical currents.
4) Type-C ports can implement optional higher-current features, for faster charging, and for powering peripherals.
5) "Alternate mode" electrical interfaces using the same host port.
6) Bi-directional current transfer capability: can be used to charge the laptop, and then later for the laptop to power/charge peripherals and smartphones.

The alternate modes is where USB-C and Mini DisplayPort connectors can get a bit tricky.

Thunderbolt 1 and 2 use the Mini-DisplayPort connector in an alternate mode, with DisplayPort running over the wire for monitors. Thunderbolt busses typically let you attach a non Thunderbolt DisplayPort monitor at the end of the device chain. TB1/2 only really saw adoption on Macs, only a handful of PCs supported it.

Thunderbolt 3 swaps to using the USB-C connector. Both Thunderbolt 2 and Thunderbolt 3 cap out at the Displayport 1.2 spec. The DP version becomes important when talking about high resolution monitors. And at this point the only devices that support TB3 are a growing number of PCs. Macs will likely ship with it later this year.

Thunderbolt is what supports device chaining, where one connector on the computer can have up to 6 devices attached to it. Normal USB over USB-C connectors still uses a hub model and not chaining.

USB-C alternate mode also allows pure DisplayPort 1.3 with no Thunderbolt. DP 1.3 adds some 5k and 8k monitor support, along with higher refresh rates for 4k monitors. DisplayPort 1.2 (and above) offers both chaining and a hub model, independent of USB or Thunderbolt.

And then there's one more way to directly drive a display over USB-C, using the MHL alternate mode. This is likely to only show up in mobile phones/tablets as this is historically where MHL has been used before and tends to be adapted into HDMI.

For Thunderbolt or DisplayPort modes over Mini DisplayPort a USB-C connector, the GPU in the computer is what is ultimately driving the monitor. Monitor and resolution limits will be decided by the built in GPU. Or to throw more complexity in, possibly by an external GPU plugged into the Thunderbolt interface (like the Razer Core). Due to Thunderbolt carrying DisplayPort, the built in LCD of a laptop could be driven by an external GPU.


And as discussed elsewhere in the thread, you then have pure USB 2.0/3.0/3.1 over USB-C, and the ability to use DisplayLink GPUs as an external GPU. Monitors plugged into these are driven directly by the DisplayLink GPU and not the computer's GPU. It's a good way to get around the limits of a built in GPU. This can come at a cost of CPU time though. Also due to normal USB not carrying a video signal over it, DisplayLink devices cannot drive an internal LCD on a laptop, only monitors directly plugged into the DisplayLink device. Oh, and don't be surprised if you come across a monitor that has a DisplayLink chip directly inside it.


It's all clear as mud. Basically for your clients Matt, you will have to know exactly what type of protocols their USB-C ports support to be able to offer a good solution. Especially if you are factoring in possible 3d graphics/gaming desires on the display. It's pretty much a non starter if DisplayLink is involved.

Thanks for all of that, Tom. This is beginning to get a lot clearer while also more confusing, but you've been helpful

The only device I'm really thinking of these days is the Dell XPS 13, which I think is the best all around Windows computer on the market. I have one and I love it. Since that will be the one I recommend, I'm going to do my best to figure out its capabilities. In general, that wouldn't include much high end 3D gaming, as much as I hear the Intel 520 is much better than previous generations.

According to Dell's product page, the port on the XPS 13 supports:

1 Thunderbolt™ 3 Supports:
Power In / Charging
PowerShare
Thunderbolt 3 (40Gbps
Bi-Directional)
USB 3.1 Gen 2 (10Gbps)
Native DisplayPort 1.2 Video
Output
VGA, HDMI, Ethernet and USB-A
via Dell Adapter (Sold Separately)

So the way that's written makes me think that there's something inherent about USB-C that enables all those connections, so why don't I see boxes with USB-C inputs and an output for every single one of the mentioned ports? Dell clearly made one and sold it until they had disastrous results with it. Why? Something tells me that the answer is "because it's the early days of the standard and these people just haven't figured it out yet." Clearly I still don't understand this connector, but I'm trying to.


But from what I understand, USB-C has a max of 40gb/s. So it's not "just a connector." I don't care if it's using USB 3 or not, I care about monitor outputs via an external breakout box in this situation. How that's done doesn't matter to me, I just want the configuration, and it seems to be something that manufacturers were also thinking about at first, but have had lots of trouble implementing.

The Dell device you mentioned seems unlikely to simply be a USB3 container. It makes me wonder what protocols it was using.

Well, USB 3.1 has a max speed of 10gbit/sec.
Thunderbolt-3 has a max speed of 40gibt/sec.

If the Thunderbolt port is using a USB-C connector, then sure.
If USB 3.1 or USB 2.0 is using a USB-C connector, then no.

It is all about the electrical protocol being used, not the connector.

EDIT: So a more correct statement would be "Thunderbolt-3 has a max of 40gb/sec, using a connector that conforms to the USB-C connector standard."

When being used for Thunderbolt-3, that port on the XPS-13 is a Thunderbolt port, not a USB port, so referring to it as USB-C creates confusion.

When that port is instead being used with USB peripherals, it is a USB 3.1 port, with a USB-C host connector.

The notebook's chipset can electrically switch modes from USB to Thunderbolt or DisplayPort, depending upon what is plugged into it.

Cheers

It occurs to me that this concept is probably a new idea to most people -- in the past, such ports mostly had a fixed electrical protocol per connector type (with allowances for some differences in USB1/2/3, or Ethernet 10/100/1000).

Microcontroller chips have long had this kind of thing -- an "Arduino" chip (ATMEGA328p) has a relatively small number of pins for communicating with the world, and most of those pins can be programmed with any of a number of radically different electrical interfaces, be it digital-in, digital-out, Analog-in, PWM-out, I2C, SPI, etc.. all on one pin.

Same basic thing, but at much much higher clock speeds!

Or maybe not. Those hubs are so cheap, I'm wondering if perhaps they actually use the "DisplayPort" signalling rather than licensing a DisplayLink chip. If they really do use DisplayPort, that would explain the low prices, and the performance should be excellent as it would be using the notebook's GPU.

http://www.laptopmag.com/articles/usb-type-c-faq

The part I am still not clear on, is whether DisplayPort can run simultaneously with USB on a single port.

EDIT: Ah, yes.. dedicated pins (kind of): http://www.vesa.org/news/vesa-brings-displayport-to-new-usb-type-c-connector/

So, yeah, that hub is probably using DisplayPort to export the native notebook GPU's output to its HDMI connector.

Having now read a lot more on these topics, I like the idea of the ThunderBolt-3 ports which use a USB-C type connector.

A "docking hub" using that connector could work in one of at least two fundamentally different ways:

(1) The hub could use USB3 protocols, with or without a DisplayPort overlay. This limits total cable bandwidth of all attached devices to the USB3.1 10gb/sec maximum throughput. Multiple USB ports require a built-in USB hub chip. Most/all stuff out there today probably works this way. If the DisplayPort feature is used simultaneously, it could occupy as much as 5.6gbit/sec of the original 10gbit/sec cable bandwidth, slowing down transfers to/from any USB3 devices on the same cable.

(2) The hub could instead use PCIe protocols, again with or without a DisplayPort overlay. This increases total cable bandwidth up to 40gb/sec for all attached devices. In order to provide one or more USB ports, a PCIe USB host adapter chip (XHCI for USB3) would be needed inside the "hub". Other PCIe host adapters could also be incorporated, giving additional "native" SATA/eSATA for example using an AHCI chip. And/or even some physical desktop machine style PCIe or PCI slots.

I get what you're saying, and I appreciate all the additional info. I guess it goes back to what I said in my last post, I don't much care how it's done, I just want what I was describing And it would be nice if it were done in the best possible way to utilize the resources of the computer. It sounds like Thunderbolt would be needed in order to create the kind of dock/hub I was talking about.

Laptops have had docking stations for ages. How have they usually done it? I assumed it wasn't on the USB bus, and was probably some sort of PCI thing. Am I wrong?


I assume that this is what I'd want. I also assume that this hub would also be much pricier than the $30-60 ones on Amazon right now.

Looks like I was right about the price. I finally stumbled across this device. It's not even slated for release until the end of next month, but it does most of what I was looking for. It's a Thunderbolt 3 dock.

The only thing that I don't like is that it says it only does a "trickle charge" for the connected laptop instead of a real charging solution. Sounds more like it maintains battery levels instead of trying to top them off.

*edit*

That Dell dock you initially linked to is also a Thunderbolt dock, but I don't know which if the scenarios you laid out either of these docks are using. But it sounds like driver support might sink these kinds of things.

Only 15W. XPS 13 has a 45W adapter so if the laptop is off it will take triple the time to charge roughly and if on will hardly charge it at all. If you were fully loading it up, it might not even be able to sustain it. Should be pretty easy to get an idea with a Kill-A-Watt type meter on the input side to the existing supply.

The Dell TB15 has a much higher power output and is a full replacement for a power supply. Unfortunately the rest of it seems badly supported by drivers/firmware/buggy hardware.

Lots of good stuff from Mark but yeah it's pretty confusing for technical people. How is it not going to be confusing for those that aren't so technical.