USB-C v. USB 3.x v. Thunderbolt 2,3,4,5

[ufgatorvet]

Noob question here, please forgive my noob-ness.

To my understanding (youtube research) ...

Known variables:
1. The new MacBook Air M4 has 2 TB4 ports.
2. I have an Apple SD card reader as well as a "SanDisk 4TB Extreme Portable SSD - Up to 1050MB/s, USB-C, USB 3.2 Gen 2" external drive.

Hypothesis: Am I correct that both of these peripherals will work with the MBA M4 due to TB backward compatibility? Am I also correct that TB4 ports can work with any USC-C 3.2 devices, but TB4 devices WILL NOT work with standard USB-C 3.2 ports?

Thanks for the response and minimal eye-rolling 😂

 

[ufgatorvet]

So sorry, posted in wrong forum. Noob move

 

[joevt]

So sorry, posted in wrong forum. Noob move

Somebody might move it.

Hypothesis: Am I correct that both of these peripherals will work with the MBA M4 due to TB backward compatibility?

Yes.

Am I also correct that TB4 ports can work with any USC-C 3.2 devices,

Yes. If it's a device that macOS has a driver for (standard USB devices, some non-standard USB devices).

but TB4 devices WILL NOT work with standard USB-C 3.2 ports?

Some Thunderbolt 4 devices can be used with standard USB-C ports. Check the specs of the Thunderbolt 4 device.

 

[ufgatorvet]

I appreciate your reply! Thank you!

 

[Anonymous Freak]

Short form:

Any Mac port that is "Thunderbolt 3", "Thunderbolt 4", or "Thunderbolt 5" (USB Type C style port with the little thunderbolt logo) will function with any Thunderbolt or USB device, although some pairings of device/Mac may not run at full speed, and there may be some "number of device" limitations. (For example, some early Apple Silicon Macs only supported one single external display via Thunderbolt, so while a Thunderbolt Display or USB-C display would work on any of the Thunderbolt ports, only one single display would work at a time.)

Any Mac port that is a "USB Type C" style port that *ISN'T* labeled with the little thunderbolt (front ports on the non-ULTRA Mac Studios, front ports on the latest-generation Mac mini,) only supports USB data, not Thunderbolt devices, not display output.

All Apple Silicon Macs support up to 10 Gbps on "non-Thunderbolt" USB devices on all USB or Thunderbolt ports.
Thunderbolt ports support Thunderbolt-specific devices up to 40 Gbps or up to 120 Gbps depending on model.

---

Long form:

USB 3+ is the absolute most confusing mess of a "standard" that has ever existed.

Wait until you hear about "USB 3.2 Gen 2 2x2"…

It's the USB standard that supports 20Gbps transfer.

Only it isn't automatic that later versions of USB support 20Gbps.

USB4, Thunderbolt 4, Thunderbolt 5 on Apple Silicon Macs don't support the "non-Thunderbolt" 20Gbps speed. To support faster than 10Gbps, the device must be a "Thunderbolt" device, not a USB device.

*SIGH*

 

[joevt]

To support faster than 10Gbps, the device must be a "Thunderbolt" device, not a USB device.

A Thunderbolt device could support "USB gen 2x2" if it contains a "USB gen 2x2" controller.

Thunderbolt 5 docks and hubs have such a USB controller built into their Thunderbolt controller but it gets bypassed by Apple Silicon Macs which use tunnelled USB from the Mac's USB 3.2 gen 2x1 controller.

USB tunnelling can be disabled by placing a Thunderbolt 3 device between the Apple Silicon Mac and the Thunderbolt 5 hub/dock.

Alternatively, a Thunderbolt 3 PCIe expansion chassis can be used to host a PCIe USB gen 2x2 XHCI controller card.

I wouldn't call USB4 a later version of USB 3.2. They're quite different. They are different specs. USB4 does include support for USB 3.2. The USB4 spec does not describe all of USB 3.2 - you need the USB 3.2 spec for that.

 

[theluggage]

I wouldn't call USB4 a later version of USB 3.2. They're quite different. They are different specs. USB4 does include support for USB 3.2. The USB4 spec does not describe all of USB 3.2 - you need the USB 3.2 spec for that.

Yup.
USB4 is the (more open) successor to Thunderbolt 3, using the same underlying 20Gbps tech - and has much the same relationship to USB 2/3/3.1/3.2 that Thunderbolt 3 did. Like TB3, it depends on USB 3.2 and other USB standards for backwards-compatibility & power delivery, but doesn't define them. C.f. TB3 it adds support for hubs with multiple downstream TB/USB4 ports and USB 3.2 tunneling.

USB4 leaves a lot of stuff - like some legacy TB1/2/3 features and multi-display support optional. Starting with TB4, Thunderbolt is effectively just an Intel branding and certification scheme for USB4 devices with a lot of the "optional" stuff made compulsory. All Apple Silicon Macs have had USB4 ports - the only reason that some MacBooks label them as "TB3/USB4" rather than TB4 is that those machines don't support at least two external displays via TB/USB4 - which is a requirement of TB4 certification.

USB4v2 adds 80Gbps speeds - TB5 is the Intel-certified version of that.

It's ridiculously confusing to punters - esp. with the USB-IFs inconsistent way of numbering standards, re-naming existing standards (USB 3.0 -> USB 3.1 gen1 etc.) and insisting on slapping the "USB" tag over everything. I know why they do it - brand recognition - but it would have been so much clearer if they'd called USB-C - oh, I dunno, "UniPlug" and USB4 "OpenBolt" (feel free to invent better names). Then there's the "latest USB standard doesn't actually require support for its major new feature" fun - which is where Thunderbolt has really come in as "The USB-C port where you can actually make some reasonable assumptions about what it supports!".

It's the USB standard that supports 20Gbps transfer.

More expansively, it's the standard that supports using two USB 3.1 channels in tandem to get a 10Gbps (2 x 5G) or 20Gbps (2 x 10G) connection. C.f. TB3 which goes up to 20Gbps per channel and can join two to get 40Gbps. I don't think its any great loss that Apple don't support it - it always looked like a dead end with Thunderbolt offering true 20Gbps, USB 3.1 still at the "good enough for most folks" stage and large chunks of the PC market still pretty wedded to USB-A ports (which can happily go up to 10G, but not 20).

 

[joevt]

More expansively, it's the standard that supports using two USB 3.1 channels in tandem to get a 10Gbps (2 x 5G) or 20Gbps (2 x 10G) connection. C.f. TB3 which goes up to 20Gbps per channel and can join two to get 40Gbps. I don't think its any great loss that Apple don't support it - it always looked like a dead end with Thunderbolt offering true 20Gbps, USB 3.1 still at the "good enough for most folks" stage and large chunks of the PC market still pretty wedded to USB-A ports (which can happily go up to 10G, but not 20).

Apple doesn't have any USB 3.2 gen 2x2 ports but does support such USB controllers since Sonoma so they can be added via PCIe card or Thunderbolt 5 dock/hub.

 

[Anonymous Freak]

I don't think its any great loss that Apple don't support it - it always looked like a dead end with Thunderbolt offering true 20Gbps, USB 3.1 still at the "good enough for most folks" stage and large chunks of the PC market still pretty wedded to USB-A ports (which can happily go up to 10G, but not 20).

For me, the only annoying part is that I do have a SanDisk USB 3.2 Gen 2 2x2 20Gbps external SSD that *IS* capable of >10Gbps; but 10Gbps is the cap on my Macs. It was quite a bit cheaper than a true Thunderbolt SSD of same capacity, and when M1 Macs came out, I saw "USB4" and naively assumed they would support 20Gbps USB 3.2.

 

[Anonymous Freak]

A Thunderbolt device could support "USB gen 2x2" if it contains a "USB gen 2x2" controller.

I was keeping it simple for my simple section, referring only to the ports on Macs.

Back in the day, I used a Thunderbolt 1 dock to add USB 3 to my iMac, it's definitely possible to use TB to add capabilities; I didn't want to go into that level of detail.

 

[ufgatorvet]

Everything after the second "Yes" in joevt's response post #3, well, you lost me. 😂

I got the answer I needed, you kids take it from here and go on and have fun!

After all, I can't even post in the correct forum, you can't expect me to spell UBS!!