Author Topic: Understanding USB-C vs Thunderbolt confusion  (Read 4803 times)

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Offline HalcyonTopic starter

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Understanding USB-C vs Thunderbolt confusion
« on: December 03, 2024, 07:16:24 am »
This seems like a simple question, but the answer doesn't appear to be completely clear. I need to order a monitor, that will work with both PC and Mac laptops (both via the USB-C "type" port).

Obviously some modern Macs have Thunderbolt interfaces, PC's don't. I need to be able to drive the display, charge the laptop and access the monitor's USB hub, all via 1 single USB-C/Thunderbolt cable.
I currently do this with a M2 MacBook Air paired with a Lenovo ThinkVision T27p10 monitor. It works a treat.

That being said, if I want to support newer MacBooks and PCs alike in the same way, do I need a monitor with USB-C input or a monitor with ThunderBolt input? From the research I've done, I need the former.

In other words will a Thunderbolt source work with a non-Thunderbolt display, or is the opposite true?

Life was much easier when if the plug fit, the thing worked.
« Last Edit: December 03, 2024, 07:20:03 am by Halcyon »
 

Offline Sorama

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #1 on: December 03, 2024, 07:39:18 am »
It does not matter.
I use a Thunderbolt output on my Mac mini to hook on to a non mac display (aoc) with usb C input.
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #2 on: December 03, 2024, 08:10:43 am »
It does not matter.
I use a Thunderbolt output on my Mac mini to hook on to a non mac display (aoc) with usb C input.

This is where the advice seems to get murky. Some say it does matter and some monitor manufacturers are producing monitors in both flavours.

The collective advice and research leads me to believe that, generally speaking:
- A Thunderbolt source will work with both a Thunderbolt and DP over USB-C monitor.
- A USB-C (non-Thunderbolt) source will only work with a USB-C monitor.

This is what I'm trying to confirm.
« Last Edit: December 03, 2024, 08:15:50 am by Halcyon »
 

Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #3 on: December 03, 2024, 08:12:42 am »
USB-C is just a connector.

If something advertises that it supports sending or receiving video over USB-C then that means it supports DisplayPort Alternate Mode. You might see a DP symbol beside the connector, but anyway if it does video then it will do DisplayPort.

Things that do Thunderbolt 3/4 over USB-C support higher speeds and the protocol is actually PCIe. Thunderbolt devices can always connect to a DP device at the other end (at lower performance).
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #4 on: December 03, 2024, 08:14:52 am »
USB-C is just a connector.

If something advertises that it supports sending or receiving video over USB-C then that means it supports DisplayPort Alternate Mode. You might see a DP symbol beside the connector, but anyway if it does video then it will do DisplayPort.

Things that do Thunderbolt 3/4 over USB-C support higher speeds and the protocol is actually PCIe. Thunderbolt devices can always connect to a DP device at the other end (at lower performance).

Thanks. I understand that and this seems to be confirming what I believe (above). So for overall compatibility, I should be choosing a USB-C/DisplayPort monitor, not Thunderbolt.
 

Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #5 on: December 03, 2024, 08:15:15 am »
Would a non-thunderbolt output work on a Thunderbolt monitor?

Yes. And a Thunderbolt output with work with a non-Thunderbolt monitor.

It's just that you only 10-20 Gbps DisplayPort speeds in both cases, not the higher 40 Gbps Thunderbolt speed.
 
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Offline abeyer

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Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #7 on: December 03, 2024, 09:57:18 am »
Thanks. I understand that and this seems to be confirming what I believe (above). So for overall compatibility, I should be choosing a USB-C/DisplayPort monitor, not Thunderbolt.

??

That doesn't follow.

I mean ... it will work with everything, but so will a monitor with Thunderbolt.

The monitor with Thunderbolt will work even better with a computer with Thunderbolt, but it will work with any computer with USB-C.

Non-Thunderbolt is usually cheaper, so if you don't need the higher performance (more pixels, more FPS) then sure DP is fine.

Either kind can be a USB-C hub to plug other devices into, but a Thunderbolt monitor will allow high transfer speeds to SSD disks etc.
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #8 on: December 03, 2024, 10:52:59 am »
PC's don't

Maybe your PC doesn't.... https://www.asus.com/us/motherboards-components/motherboards/accessories/thunderboltex-4/

OK sure. You can buy Thunderbolt expansion cards. I'm specifically talking about laptops.

Thanks. I understand that and this seems to be confirming what I believe (above). So for overall compatibility, I should be choosing a USB-C/DisplayPort monitor, not Thunderbolt.

??

That doesn't follow.

I mean ... it will work with everything, but so will a monitor with Thunderbolt.

The monitor with Thunderbolt will work even better with a computer with Thunderbolt, but it will work with any computer with USB-C.

Non-Thunderbolt is usually cheaper, so if you don't need the higher performance (more pixels, more FPS) then sure DP is fine.

Either kind can be a USB-C hub to plug other devices into, but a Thunderbolt monitor will allow high transfer speeds to SSD disks etc.


I've read reports of interoperability issues with each other. It seems to be the case of "it depends".
 

Offline Someone

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #9 on: December 03, 2024, 11:14:33 am »
PC's don't
Maybe your PC doesn't.... https://www.asus.com/us/motherboards-components/motherboards/accessories/thunderboltex-4/
OK sure. You can buy Thunderbolt expansion cards. I'm specifically talking about laptops.
So the original statement:
Obviously some modern Macs have Thunderbolt interfaces, PC's don't.
Pretty much all of that is exaggeration/incorrect:
Every single mac shipping right now has thunderbolt (not some).
Many "PC" laptops have thunderbolt, even cheaper business tier portables (and pretty much all workstations).
It has been this way for years.

Recent USB versions are subsets of Thunderbolt, but for backwards compatibility USB-C monitors are more universal.
 
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Offline Sorama

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #10 on: December 03, 2024, 11:37:40 am »
Actually, Thunderbolt was developed by Apple and Intel (intel now has all the rights) and in the beginning (v1 & v2) was used by means of a DisplayPort cable.

Thunderbolt v3 uses a usb C cable and is able to not only transfer audio and image, but also data.
« Last Edit: December 03, 2024, 11:51:31 am by Sorama »
 
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Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #11 on: December 03, 2024, 11:40:24 am »
PC's don't
Maybe your PC doesn't.... https://www.asus.com/us/motherboards-components/motherboards/accessories/thunderboltex-4/
OK sure. You can buy Thunderbolt expansion cards. I'm specifically talking about laptops.
So the original statement:
Obviously some modern Macs have Thunderbolt interfaces, PC's don't.
Pretty much all of that is exaggeration/incorrect:
Every single mac shipping right now has thunderbolt (not some).
Many "PC" laptops have thunderbolt, even cheaper business tier portables (and pretty much all workstations).
It has been this way for years.

Recent USB versions are subsets of Thunderbolt, but for backwards compatibility USB-C monitors are more universal.

You are correct. And I stand corrected, even my M2 Mac which I still consider current, has Thunderbolt 3.

The issue is, I do have older PC laptops which whilst superseded by today's standards, are still in use. I need to cater for those. Those definitely don't have Thunderbolt, so I'm looking for the best of both worlds. None of this is going to be used for gaming, so anything above 60hz is mostly pointless.
 

Offline ejeffrey

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #12 on: December 03, 2024, 05:46:57 pm »
In any case: thunderbolt displays will work with USB type C ports that support video and USB-C monitors work with thunderbolt hosts.

The only issue with USB type C is that the max bandwidth is less and also can be partitioned less flexibly than thunderbolt.  This makes thunderbolt better for multi monitor and docking stations where you want multiple high speed devices sharing the link.
 

Offline Squarewave

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #13 on: December 03, 2024, 07:16:54 pm »
Some modern PCs have thunderbolt, my HP does.
 

Offline IanB

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #14 on: December 03, 2024, 07:25:46 pm »
OK sure. You can buy Thunderbolt expansion cards. I'm specifically talking about laptops.

My Dell laptop has two Thunderbolt 4 ports and also a USB-C port with DP-alt mode.
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #15 on: December 04, 2024, 06:33:27 am »
OK sure. You can buy Thunderbolt expansion cards. I'm specifically talking about laptops.

My Dell laptop has two Thunderbolt 4 ports and also a USB-C port with DP-alt mode.

Seems it's more popular than I originally thought. I concede.
 

Online tooki

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #16 on: December 04, 2024, 09:02:17 am »
Obviously some modern Macs have Thunderbolt interfaces, PC's don't. I need to be able to drive the display, charge the laptop and access the monitor's USB hub, all via 1 single USB-C/Thunderbolt cable.
Many PCs today have Thunderbolt, too — Thunderbolt is developed primarily by Intel, after all! Consequently it’s very common on PCs with Intel chipsets. It is much rarer on AMD chipsets.

Anyhow, what you want is no problem. A Thunderbolt 3 or 4 port is also USB-C.

A Thunderbolt device (disk array, display, etc) works only on a Thunderbolt-equipped computer. But a USB-C display will work on USB-C ports and Thunderbolt-enabled USB-C ports.

(AFAIK, USB 4 largely eliminates this distinction, as it formally incorporates Thunderbolt into USB. I think there are some minor differences. I’d have to look into it more.)
 

Online tooki

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #17 on: December 04, 2024, 09:05:53 am »
Thanks. I understand that and this seems to be confirming what I believe (above). So for overall compatibility, I should be choosing a USB-C/DisplayPort monitor, not Thunderbolt.

??

That doesn't follow.

I mean ... it will work with everything, but so will a monitor with Thunderbolt.

The monitor with Thunderbolt will work even better with a computer with Thunderbolt, but it will work with any computer with USB-C.
It probably depends on the precise implementation, but my understanding is that Thunderbolt displays fundamentally cannot be expected to work on a “plain” USB-C port.
 

Offline tszaboo

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #18 on: December 04, 2024, 09:56:56 am »
I have a Thunderbolt dock at home, that I use with my work laptop. I plugged in my home laptop that only has USB-C, USB 3.1 or something into it. It was one of this: "I wonder if it works" questions. It did. And then when I disconnected it the laptop BSOD. So I suggest getting compatible things and don't rely on chance and other people experience.
 

Offline Someone

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #19 on: December 04, 2024, 10:06:44 am »
don't rely on chance and other people experience.
Other peoples experience, when that is specific model of computer and specific model of peripheral is often the best thing to rely on!
 

Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #20 on: December 04, 2024, 10:24:19 am »
According to internet, Apple's 27" 5K Studio display, for example, works with non-Apple PCs with ThunderBolt 3/4 at 5120x2680 @60 but will also work at lower resolution with DP Alt Mode on USB-C.
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #21 on: December 04, 2024, 11:02:37 am »
According to internet, Apple's 27" 5K Studio display, for example, works with non-Apple PCs with ThunderBolt 3/4 at 5120x2680 @60 but will also work at lower resolution with DP Alt Mode on USB-C.

For the price of an Apple Studio display, I'd expect it to do that as a minimum, and make me coffee in the morning!
 

Offline tszaboo

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #22 on: December 04, 2024, 11:33:19 am »
don't rely on chance and other people experience.
Other peoples experience, when that is specific model of computer and specific model of peripheral is often the best thing to rely on!
Until you get a firmware or windows or apple update and it breaks it all.
« Last Edit: December 04, 2024, 11:40:04 am by tszaboo »
 

Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #23 on: December 04, 2024, 11:46:20 am »
According to internet, Apple's 27" 5K Studio display, for example, works with non-Apple PCs with ThunderBolt 3/4 at 5120x2680 @60 but will also work at lower resolution with DP Alt Mode on USB-C.

For the price of an Apple Studio display, I'd expect it to do that as a minimum, and make me coffee in the morning!

It's worth getting a good monitor. It's what your eyes are looking at 8 or 12 or 16 hours a day. It's something you can use for a decade or more, with as many different computer upgrades as you want.
 

Offline Postal2

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #24 on: December 04, 2024, 12:02:52 pm »
... It's worth getting a good monitor. It's what your eyes are looking at 8 or 12 or 16 hours a day. ...
You know my monitor. I recently checked my vision on an automatic machine, it turned out to be not very good, namely 0.45/0.75 (correction no/yes). But I don't feel discomfort and don't wear glasses.
 

Offline ejeffrey

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #25 on: December 04, 2024, 09:03:08 pm »

The monitor with Thunderbolt will work even better with a computer with Thunderbolt, but it will work with any computer with USB-C.
It probably depends on the precise implementation, but my understanding is that Thunderbolt displays fundamentally cannot be expected to work on a “plain” USB-C port.
[/quote]


This is not my understanding.  Thunderbolt's data communication protocol for devices like storage arrays and external GPUs is basically PCIe, but that is not what used for displays.  Even with thunderbolt, display port is it's own alternate mode which is superset of the regular USB-C display port alt mode.  I don't know for sure if it's required by the standard to be backwards compatible with USB-C, but the handful of thunderbolt monitors I am aware of work with USB-C.

 

Offline IanB

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #26 on: December 04, 2024, 10:44:10 pm »
This is not my understanding.  Thunderbolt's data communication protocol for devices like storage arrays and external GPUs is basically PCIe, but that is not what used for displays.  Even with thunderbolt, display port is it's own alternate mode which is superset of the regular USB-C display port alt mode.  I don't know for sure if it's required by the standard to be backwards compatible with USB-C, but the handful of thunderbolt monitors I am aware of work with USB-C.

Doesn't it depend on whether the USB-C port actually supports DP-alt mode? There may be some that don't.
 
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Online tooki

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #27 on: December 04, 2024, 10:55:40 pm »
... It's worth getting a good monitor. It's what your eyes are looking at 8 or 12 or 16 hours a day. ...
You know my monitor. I recently checked my vision on an automatic machine, it turned out to be not very good, namely 0.45/0.75 (correction no/yes). But I don't feel discomfort and don't wear glasses.
0.45/0.75 diopters? If so that’s absolutely nothing.
 

Online The Soulman

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #28 on: December 04, 2024, 10:56:20 pm »
For a professional use (thunderbolt..) docking station I can recommend the products from Sonnet:
https://www.sonnettech.com/home.html

They also have compatibility charts and appear to do some products that support "displaylink" basically a external graphics card over USB 3?
https://www.sonnettech.com/product/usbc-to-dual-4k-60hz-hdmi-adapter/overview.html
 

Offline ejeffrey

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #29 on: December 05, 2024, 12:59:52 am »
Doesn't it depend on whether the USB-C port actually supports DP-alt mode? There may be some that don't.

Yes for sure.  If the port doesn't support display port output it doesn't matter what kind of display you hook up to it.

The question was about compatibility for USB-C vs thunderbolt monitors.  And as far as I know either will work as long as you connect it to a video capable port, whether it is thunderbolt or not.
 

Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #30 on: December 05, 2024, 02:03:14 am »
Doesn't it depend on whether the USB-C port actually supports DP-alt mode? There may be some that don't.

Yes for sure.  If the port doesn't support display port output it doesn't matter what kind of display you hook up to it.

The question was about compatibility for USB-C vs thunderbolt monitors.  And as far as I know either will work as long as you connect it to a video capable port, whether it is thunderbolt or not.

Right. You have to check the specs!

I just looked at my Lenovo Legion Pro 5i 16" Gen 8 (2023), which I've never really paid attention to the ports as I only ever used the HDMI and an always-on USB A to charge my phone. The main reason I got it is the mighty 24 core i9-13900HX CPU (with 32 GB RAM and low end 4060 GPU) and it was cheap (US$1500+tax) as the Gen 9 were already out.

Back:

- USB-C 3.2 Gen 2 PD (support data transfer, Power Delivery 140W and DisplayPort 1.4)

- USB A 3.2 Gen 1

- USB A 3.2 Gen 1 (always on)

Left side:

- USB A 3.2 Gen 1

- USB-C 3.2 Gen 2 (support data transfer and DisplayPort 1.4)

Right side:

- USB A 3.2 Gen 1

Don't confuse PD with DP, though it seems at least in this case PD includes DP :)

It seems both USB-C ports support up to 5k @60Hz without Data Stream Compression. I don't know whether DSC is supported -- that would enable up to 8k monitors. Actually I'm guessing since the HDMI supports 8k then the USB-C probably does too?

(not listed above for conciseness: RJ-45 gigE, full size HDMI 2.1 (up to 8K/60Hz), traditional 20V 300W power, 3.5mm headphone/mic, Wi-Fi 6E, 802.11ax 2x2 Wi-Fi + Bluetooth 5.2)
 

Offline Someone

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #31 on: December 05, 2024, 05:38:57 am »
This is not my understanding.  Thunderbolt's data communication protocol for devices like storage arrays and external GPUs is basically PCIe, but that is not what used for displays.  Even with thunderbolt, display port is it's own alternate mode which is superset of the regular USB-C display port alt mode.  I don't know for sure if it's required by the standard to be backwards compatible with USB-C, but the handful of thunderbolt monitors I am aware of work with USB-C.

Doesn't it depend on whether the USB-C port actually supports DP-alt mode? There may be some that don't.
Worse, thunderbolt controllers don't always support the negotiation and formats that USB do.

ComputerMonitor/Dock
ThunderboltThunderboltOk
ThunderboltUSB-C + DP altmodeOk
USB-C + DP altmodeUSB-C + DP altmodeOk
USB-C + DP altmodeThunderboltFail

Had a visitor to the office today which enabled testing that last combination with a recent entry level business laptop. Windows 11 identified it was seeing a thunderbolt peripheral and popped up a warning with a link to further information. Pretty slick. PD still negotiated charging for the laptop but no USB downstream or Video connected.
 
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Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #32 on: December 05, 2024, 06:18:37 am »
USB-C + DP altmodeThunderboltFail

Had a visitor to the office today which enabled testing that last combination with a recent entry level business laptop. Windows 11 identified it was seeing a thunderbolt peripheral and popped up a warning with a link to further information. Pretty slick. PD still negotiated charging for the laptop but no USB downstream or Video connected.

It's supposed to work. Does your monitor's manufacturer say it works? Can you name names?
 

Offline Postal2

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #33 on: December 05, 2024, 08:39:35 am »
......0.45/0.75 diopters? If so that’s absolutely nothing.
I just looked, it turns out that in different countries visual acuity is determined differently. I don't know what the device is called, but you put your head in there, and it shows a little plane behind the lens, everything moves automatically, and then a tape with printed results comes out. Apparently, the device is adapted to the country in which it is used.
Quote
In the Commonwealth of Independent States (CIS), visual acuity is measured in fractions of a unit: 1.0 is normal vision, 0.9, 0.8 … 0.1 is determined by the number of lines starting from the top on the Sivtsev or Golovin table from a distance of five meters (0.1 if the eye sees only the top row; 2.0 if the bottom row is visible; normal vision (1.0) is when a person sees the tenth line with each eye from a distance of five meters). Research is carried out for each eye separately: first, the visual acuity of one eye is determined, then the other.
The problem is that a person can easily memorize the chart and cheat, hoping to get a job where visual acuity matters. It is impossible to cheat an automatic device.


The quality of my vision, which I have given above, indicates that even with glasses (correction) I will not see the line of text that a person with normal vision should see. However, I can easily read small print on products in a store.


At a distance of 5 meters, a person with normal vision (not me) can distinguish 2 stripes, spaced 1.2 mm apart. Let's assume a sufficient pixel size of 0.1 mm and multiply by 5120. We get 5 meters. We recalculate the diagonal of 27 into a horizontal of ~22. The horizontal is ~55 cm. The viewing distance is 55 cm. Apple calculated everything correctly. If I had the same sharp vision as brucehoult, I would probably plan to buy such a display.
« Last Edit: December 05, 2024, 10:45:49 am by Postal2 »
 

Offline Someone

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #34 on: December 05, 2024, 10:20:05 am »
USB-C + DP altmodeThunderboltFail

Had a visitor to the office today which enabled testing that last combination with a recent entry level business laptop. Windows 11 identified it was seeing a thunderbolt peripheral and popped up a warning with a link to further information. Pretty slick. PD still negotiated charging for the laptop but no USB downstream or Video connected.
It's supposed to work. Does your monitor's manufacturer say it works? Can you name names?
Why is it supposed to work? The thunderbolt endpoint(s) specifically call out in their documentation packages that a USB-C source is insufficient, only a thunderbolt source will work but that thunderbolt is backward-forwards compatible.

I'm not sure there was any backwards Thunderbolt compatibility built into USB specs, just that USB4 is a subset of Thunderbolt 4 and shares protocols/pinout/negotiation.
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #35 on: December 05, 2024, 10:41:42 am »
This is not my understanding.  Thunderbolt's data communication protocol for devices like storage arrays and external GPUs is basically PCIe, but that is not what used for displays.  Even with thunderbolt, display port is it's own alternate mode which is superset of the regular USB-C display port alt mode.  I don't know for sure if it's required by the standard to be backwards compatible with USB-C, but the handful of thunderbolt monitors I am aware of work with USB-C.

Doesn't it depend on whether the USB-C port actually supports DP-alt mode? There may be some that don't.
Worse, thunderbolt controllers don't always support the negotiation and formats that USB do.

ComputerMonitor/Dock
ThunderboltThunderboltOk
ThunderboltUSB-C + DP altmodeOk
USB-C + DP altmodeUSB-C + DP altmodeOk
USB-C + DP altmodeThunderboltFail

Had a visitor to the office today which enabled testing that last combination with a recent entry level business laptop. Windows 11 identified it was seeing a thunderbolt peripheral and popped up a warning with a link to further information. Pretty slick. PD still negotiated charging for the laptop but no USB downstream or Video connected.

This seems to be accurate based on the research I've done and people I've spoken to. I ended up going with the USB-C version of the monitor and it works perfectly with all the machines, including modern Macs with Thunderbolt.

Seems like this is the way to go to be on the safe side.

Thanks everyone for their input.
 

Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #36 on: December 05, 2024, 11:30:28 am »
USB-C + DP altmodeThunderboltFail

Had a visitor to the office today which enabled testing that last combination with a recent entry level business laptop. Windows 11 identified it was seeing a thunderbolt peripheral and popped up a warning with a link to further information. Pretty slick. PD still negotiated charging for the laptop but no USB downstream or Video connected.
It's supposed to work. Does your monitor's manufacturer say it works? Can you name names?
Why is it supposed to work? The thunderbolt endpoint(s) specifically call out in their documentation packages that a USB-C source is insufficient, only a thunderbolt source will work but that thunderbolt is backward-forwards compatible.

I've already pointed out that Apple's materials say their Thunderbolt monitors work on computers with USB-C DP.

Obviously I believe you that the device you have doesn't work, but why are you reluctant to say what it is, so that others can avoid it?
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #37 on: December 05, 2024, 12:34:28 pm »
USB-C + DP altmodeThunderboltFail

Had a visitor to the office today which enabled testing that last combination with a recent entry level business laptop. Windows 11 identified it was seeing a thunderbolt peripheral and popped up a warning with a link to further information. Pretty slick. PD still negotiated charging for the laptop but no USB downstream or Video connected.
It's supposed to work. Does your monitor's manufacturer say it works? Can you name names?
Why is it supposed to work? The thunderbolt endpoint(s) specifically call out in their documentation packages that a USB-C source is insufficient, only a thunderbolt source will work but that thunderbolt is backward-forwards compatible.

I've already pointed out that Apple's materials say their Thunderbolt monitors work on computers with USB-C DP.

Obviously I believe you that the device you have doesn't work, but why are you reluctant to say what it is, so that others can avoid it?

Sure, Apple's monitors might, but what about other manufacturers? I'm not purchasing Apple monitors.

I don't have a monitor that "doesn't work". I was looking at a new display to replace the ones I had. The research didn't seem so simple (that's evident just in the comments in this thread). I ended up going with the Samsung USB-C models and they work great.

Monitor manufacturers seem reluctant saying that it works with certain machines because of these incompatibilities. You won't find it anywhere in the Samsung specs, for example. There was a reason behind my original question because it's not straightforward. I wasn't about to spend good money on something that didn't work, because I didn't do my homework properly.

@Someone provided a real world example showcasing this issue. That's not to say all USB-C DP sources will fail on a Thunderbolt monitor, because that's not always the case either. I was looking for the path of least resistance, and a monitor that worked the best in most situations.
« Last Edit: December 05, 2024, 12:49:45 pm by Halcyon »
 
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Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #38 on: December 05, 2024, 01:36:36 pm »
I've already pointed out that Apple's materials say their Thunderbolt monitors work on computers with USB-C DP.

Obviously I believe you that the device you have doesn't work, but why are you reluctant to say what it is, so that others can avoid it?

Sure, Apple's monitors might, but what about other manufacturers? I'm not purchasing Apple monitors.

I just checked the manual for LG's 27" 5k Thunderbolt monitor, which internet says is comparable to Apple's in quality but much cheaper, and is much better than Samsung's.

https://gscs-b2c.lge.com/downloadFile?fileId=s9rQnprzSnnnuCWBNL5gBQ

It explicitly says it supports connecting the "Thunderbolt" input port to USB-C DP on Windows 10 machines, though you get only 4k resolution. Apparently they supply different cables in the box for Thunderbolt and USB-C connection to the same port on the monitor.

The manual for the Samsung 27" Smart Monitor Viewfinity S9 S90PC 5K says: "Connects to a source device using a USB Type-C cable. When connecting a USB Type-C source device, make sure to use the USB Type-C 3.1 Gen2 10G cable so that the screen is displayed properly. Lower version cables do not support the video input function (Displayport ALT)." The illustration on P25 shows that, again, separate Thunderbolt and USB-C cables are supplied but that they both plug into the Thunderbolt port on the monitor.

The manual says the S9 series support 5k from both Thunderbolt and USB-C sources.

https://downloadcenter.samsung.com/content/UM/202402/20240228042159001/BN81-24425G-02_WEB_M50C%20M70C%20M80C%20S90PC_ASIA%20MENA%20AFRICA_L06_240226.1.zip

2453999-0

So that's at least Apple, LG, and Samsung supporting USB-C DP on their Thunderbolt monitors.

Quote
Monitor manufacturers seem reluctant saying that it works with certain machines because of these incompatibilities. You won't find it anywhere in the Samsung specs, for example. There was a reason behind my original question because it's not straightforward. I wasn't about to spend good money on something that didn't work, because I didn't do my homework properly.

See above for my homework results.

Quote
@Someone provided a real world example showcasing this issue.

No they didn't.

They said some unspecified device failed, under some unspecified conditions.

As they have not said which device we can not:

1) avoid that device

2) check the manuals to see whether they claim compability and there was perhaps user error
« Last Edit: December 05, 2024, 01:39:45 pm by brucehoult »
 
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Offline Postal2

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #39 on: December 05, 2024, 03:19:35 pm »
I have a usb adapter compatible with Windows XP (photo). Of course, not USB-C, but almost. All that's left is to buy a monitor.
 

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #40 on: December 05, 2024, 08:21:55 pm »
2) check the manuals to see whether they claim compability and there was perhaps user error
That's it, way too much reading to find some short line that is almost ambiguous (who remembers all the USB x.y n.m gen r combinations?) statement.

The two thunderbolt endpoints I have here (and others) say in the manual that only thunderbolt works for a source. I was able to verify that a random newer USB standard did not negotiate anything beyond the PD.
Will zero USB devices negotiate with those endpoints? perhaps, I can't claim that at this time.
Will all USB devices work on all Thunderbolt monitors? No, I found the example to prove that is untrue.... and it is supported by the documentation.

Are there other Thunderbolt endpoints that also support USB sources? Yes, some even advertise clearly that they are universal.

But Thunderbolt alone is not always downward/sideways compatible with USB. From my tests, and from the documentation of manufacturers. Unless someone can find a Thunderbolt specification document somewhere that says it must accept USB encapsulated sources (of some format) then I'm siding with the manufacturers in saying Thunderbolt is just that and no more.

Given the OP is asking for a solution that isn't full of corner cases and "might work might not" then the advice has been pretty much on the money, get a monitor that explicitly states it will do USB DP altmode, I'm yet to find a laptop that advertises video out on a USB-C connector which couldn't connect to that sort of end point (still does not mean 100%, but better than the cases which I can very quickly find failing examples of).
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #41 on: December 05, 2024, 10:12:51 pm »
The other thing is, I don't want multiple cables. I want one cable that will work with all machines.
 

Offline brucehoult

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #42 on: December 05, 2024, 11:43:05 pm »
2) check the manuals to see whether they claim compability and there was perhaps user error
That's it, way too much reading to find some short line that is almost ambiguous (who remembers all the USB x.y n.m gen r combinations?) statement.

The two thunderbolt endpoints I have here (and others) say in the manual that only thunderbolt works for a source. I was able to verify that a random newer USB standard did not negotiate anything beyond the PD.

And you STILL haven't told us what these "two thunderbolt endpoints" are, which makes your information not useful to anyone.

Quote
Given the OP is asking for a solution that isn't full of corner cases and "might work might not" then the advice has been pretty much on the money, get a monitor that explicitly states it will do USB DP altmode

Which is the case for Thunderbolt monitors from all manufacturers I checked: Apple, LG, and Samsung.

Perhaps there are one or more 2nd tier brands where it is not true, but I'm unlikely to buy a monitor from outside that trio, and I don't have time or inclination to check all others -- unless at some point I'm in the market for a monitor and see a particularly interesting deal, in which case I will check exactly that one.
 

Offline Postal2

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #43 on: December 12, 2024, 03:30:54 pm »
I just discovered USB-C wear when charging a 3 year old tablet. I had no issues with micro USB for 10 years. The USB-C wear was that the tablet was not getting enough current when charging from 0%, the charging started in cycles, I waited 15 minutes. Then I turned the USB-C over and it started charging normally. I suspect the whole USB-C thing is a world class scam.


Confirming the problem is easy even for a schoolchild. Open the device that will receive a large current. Connect USB-C and look at the heating of the USB-C socket with a thermal imager. After that, draw a conclusion about the durability.
« Last Edit: December 12, 2024, 04:45:40 pm by Postal2 »
 

Offline IanB

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #44 on: December 12, 2024, 04:41:40 pm »
I just discovered USB-C wear when charging a 3 year old tablet. I had no issues with micro USB for 10 years. The USB-C wear was that the tablet was not getting enough current when charging from 0%, the charging started in cycles, I waited 15 minutes. Then I turned the USB-C over and it started charging normally. I suspect the whole USB-C thing is a world class scam.

I have had issues like that with charging iPhones and the Lightning connector. It happens that dust and fluff can accumulate in the connector port and create poor electrical contact.

With the Lightning connector the electrical contacts on the plug and socket are open and accessible, and very easy to clean with a toothpick or some other implement.

With the USB-C connector the electrical contacts are buried and hard to reach with any cleaning implements. I'm not sure what the best cleaning method might be, compressed air maybe?

Anyway, I think the Lighting design is more robust than USB-C in this regard.
 

Offline Postal2

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #45 on: December 12, 2024, 05:01:12 pm »
... It happens that dust and fluff can accumulate in the connector port and create poor electrical contact. ...
I've added to the previous post. No, the cord is always in the same position in a clean place where the tablet is placed to charge. It has probably been through ~1000 connection cycles in the same position. At each stage I reconnected it several times. It took some effort to turn it over, and it worked immediately. The tablet is used only at home, and it runs out of battery because I sometimes fall asleep with it on.


At the moment, I marked the top of the USB-C plug with a cross so as not to mix it up. Before that, I noticed that the tablet sometimes takes longer to charge than usual.
I assume that the nickel coating on the contacts has worn off and degraded. And if you think that it is thick enough on your cable, perhaps this can be checked chemically. Buy the cheapest connector on Aliexpress, disassemble both connectors, leaving only the contacts and put them in acid, which eats nickel. I assume that the nickel dissolution time will be the same, unless the sellers of your expensive cable bought connectors from the absolute garbage that they usually find.
« Last Edit: December 12, 2024, 05:49:17 pm by Postal2 »
 

Online tooki

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #46 on: December 13, 2024, 11:50:53 am »
I have had issues like that with charging iPhones and the Lightning connector. It happens that dust and fluff can accumulate in the connector port and create poor electrical contact.

With the Lightning connector the electrical contacts on the plug and socket are open and accessible, and very easy to clean with a toothpick or some other implement.

With the USB-C connector the electrical contacts are buried and hard to reach with any cleaning implements. I'm not sure what the best cleaning method might be, compressed air maybe?

Anyway, I think the Lighting design is more robust than USB-C in this regard.
In a way yes. But there’s also a strong argument for having the “consumable” part of a connector pair — the spring side — on the cable and not in the device.

I suppose the counterargument is that having the springs in the device means a device maker will choose a connector with robust, long-lasting springs, whereas a cable maker may choose el-cheapo connectors with lousy springs that lose force.
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #47 on: December 15, 2024, 10:33:42 am »
I have had issues like that with charging iPhones and the Lightning connector. It happens that dust and fluff can accumulate in the connector port and create poor electrical contact.

With the Lightning connector the electrical contacts on the plug and socket are open and accessible, and very easy to clean with a toothpick or some other implement.

With the USB-C connector the electrical contacts are buried and hard to reach with any cleaning implements. I'm not sure what the best cleaning method might be, compressed air maybe?

Anyway, I think the Lighting design is more robust than USB-C in this regard.
In a way yes. But there’s also a strong argument for having the “consumable” part of a connector pair — the spring side — on the cable and not in the device.

I suppose the counterargument is that having the springs in the device means a device maker will choose a connector with robust, long-lasting springs, whereas a cable maker may choose el-cheapo connectors with lousy springs that lose force.

This seems to be the case with older Apple products. Poor connectivity was either due to junk in the receptacle (on the device) and/or poor quality cables (even the Apple genuine ones were a bit crap).

I've had far fewer issues with USB connectors over the past several years. Anecdotally, I probably replaced 1 USB socket for every 20 Apple lightning connectors.
 

Online tooki

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #48 on: December 15, 2024, 08:17:34 pm »
For sure, Apple’s switch to PVC-free cables (around 2010 I think?) led to years of cables with poor longevity. (Like the insulation seemingly growing in length over time, causing it to buckle and eventually split open, splintering lengthwise at strain points.) It took a long time for them to find something that works. And even now I’d argue that PVC insulation still holds up better.

The very first generation of lightning plugs was susceptible to the same failure mode that affects many USB-C and HDMI plugs (and nearly all full-size DisplayPort plugs) today: snapping off of the little PCB the connector straddles, if the plug housing is subjected to any force. They quickly changed that to a better design that is well-supported, and that problem vanished. (Both in Apple cables and in authorized third-party cables, since Apple supplies all Lightning plugs for those.)

At some point much later on, they changed the plating of the contacts from gold to rhodium to better resist arcing damage from hot-plugging. A super common failure mode was for arcing to damage the gold plating, and then for moisture and finger oils to provide a path for electrolytic corrosion. (Since the contacts on the lightning plug are completely exposed, it’s very easy for them to become contaminated.) Look at many a well-used lightning plug and you’ll see one contact per side that is corroded while the others are largely intact; that’s the 5V contact.

While I can’t verify it, I assume the 5V pins in the connectors also have more corrosion, due to contaminants transferred from the plugs.

This question never occurred to me before, but I wonder if this a contributing reason to why USB-C was designed with all its contacts recessed, even though it makes the plug a bit fatter.
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #49 on: December 16, 2024, 01:33:36 am »
Just a brief update, it looks like it's possible to run the monitor I purchased at 3440x1400 @ 100hz using DP over USB-C in "high resolution" mode, at the expense of a speed reduction over the built-in USB hub and ethernet port.

 
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Offline Someone

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #50 on: December 16, 2024, 04:39:26 am »
Just a brief update, it looks like it's possible to run the monitor I purchased at 3440x1400 @ 100hz using DP over USB-C in "high resolution" mode, at the expense of a speed reduction over the built-in USB hub and ethernet port.
So the DP takes over all the signalling on the high speed pairs and the USB connection drops back to a USB-2 ?
 

Offline HalcyonTopic starter

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Re: Understanding USB-C vs Thunderbolt confusion
« Reply #51 on: December 16, 2024, 06:25:10 am »
Just a brief update, it looks like it's possible to run the monitor I purchased at 3440x1400 @ 100hz using DP over USB-C in "high resolution" mode, at the expense of a speed reduction over the built-in USB hub and ethernet port.
So the DP takes over all the signalling on the high speed pairs and the USB connection drops back to a USB-2 ?

I'm not entirely sure. I haven't had time to do proper testing with some high speed SSDs. I probably won't get to it this year, but when I do, I'll report my findings.

Even if it is USB 2.0 speeds, that's perfectly fine. The hub in the monitor is only being used for keyboard, mouse and a webcam. Any drives generally get plugged directly into the machine itself and the ethernet port isn't being used as Wi-Fi is faster.
 


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