Thunderbolt 3, 4, or USB-C Cable? Which is the right choice?

[snak-atak]

This whole USB-C / Thunderbolt cable standards has me all confused. I am trying to figure out what the differences are between the Thunderbolt 4, Thunderbolt 3, and USB-C cables are, and what are the use cases between each cable?

As a bit of background, I have the Studio w/ M1 Max. Attached to it is the LG 5k display, a couple of Dell 1080P monitors, and two external SSD drives. I also own a 16" MacBook Pro 2019, an M1 MacBook Air, an M1 13" MacBook pro, and an 2019 13" MacBook Pro. Or rather, I should say that I purchased these for my family over the years. I also have a couple of iPads including the 12.9" M1 iPad Pro, and of course a few iPhones. I want to make sure that I am not limiting my investments by purchasing the wrong cables but I don't know what's the difference between the USB-C cables and advertised Thunderbolt cables. Both say that they charge up to 100w, but the Thunderbolt cables cost twice as much. What's really the difference, and what do I lose out on if I get the USB-C cables?

 

[joevt]

• Thunderbolt 4 - connect anything (DisplayPort, USB, Thunderbolt).
• Thunderbolt 3 (40 Gbps, passive cable - short: 0.8 m) - connect anything.
• Thunderbolt 3 (20 Gbps cable) - connect anything. 20 Gbps means it's probably passive.
• Thunderbolt 3 (40 Gbps, active cable - long: 1m - 2m) - connect Thunderbolt devices. Maybe USB 2.0. Not USB 3.x or DisplayPort (except the Apple Thunderbolt 3 Pro cable which is probably more like a Thunderbolt 4 cable https://support.apple.com/en-ca/HT210997 )
• USB-C (10 Gbps data cable) - connect anything (but Thunderbolt only connects at 20 Gbps speed).
• USB-C (5 Gbps data cable) - I think these exist? Don't use these for DisplayPort or Thunderbolt (well, DisplayPort may work at HBR link rate and maybe HBR2 link rate).
• USB-C (charging cable) - connect only USB 2.0 480 Mb/s. No DisplayPort or Thunderbolt.

LG UltraFine 5K requires Thunderbolt (40 Gbps) cable for full 5K60. A 20 Gbps cable Thunderbolt cable or 10 Gbps USB-C cable will limit you to 4K60 or 5K39.
1080P monitors can use USB-C 5 Gbps cable up to maybe 150Hz.

• Thunderbolt 3/4: 20.625 Gbps per line, 2 lines per lane (for transmit and receive), two lanes; aggregated = 41.25 Gbps.
• Thunderbolt 2: 10.3125 Gbps per line, 2 lines per lane (for transmit and receive), two lanes; aggregated = 20.625 Gbps.
• Thunderbolt 1: 10.3125 Gbps per line, 2 lines per lane (for transmit and receive), two lanes; no aggregation = 10.3125 Gbps x 2.
• DisplayPort HBR = 2.7 Gbps 1,2,4 lanes, one line per lane for transmit only; max = 10.8 Gbps.
• DisplayPort HBR2 = 5.4 Gbps 1,2,4 lanes, one line per lane for transmit only; max = 21.6 Gbps.
• DisplayPort HBR3 = 8.1 Gbps 1,2,4 lanes, one line per lane for transmit only; max = 32.4 Gbps.
• USB 3.1 gen 2 = 10 Gbps (two lines, one for transmit and another for receive).
• USB 3.0 = 5 Gbps (two lines, one for transmit and another for receive).
• USB 2.0 = 480 Mb/s uses separate high speed line of the USB-C cable; the same line is used for transmit and receive.

You can mix DisplayPort with USB for USB displays or docks:

• USB 2.0 with 4 lanes of DisplayPort.
• USB 3.x with 2 lanes of DisplayPort.

Each line is two wires (for differential signalling).

Everything other than USB 2.0 uses up to 4 SuperSpeed lines of the USB-C cable.

USB4 is similar to Thunderbolt but uses 10 Gbps or 20 Gbps on the wires when connected to USB4 devices instead of Thunderbolt devices.

The signal on the SuperSpeed wires uses an encoding scheme which uses extra bits to help with DC-balance, bounded disparity, clock recovery. This reduces the amount of actual data that can be transmitted.

• Thunderbolt: 64b/66b
• DisplayPort: 8b/10b
• USB4 40 Gbps: 128b/132b
• USB4 20 Gbps: 64b/66b
• USB 3.1 gen 2: 128b/132b
• USB 3.0: 8b/10b

Different cables support different amount of charging. I think the minimum is 15W. Thunderbolt 4 cables are always 100W.

 

[snak-atak]

Thunderbolt 4 - connect anything (DisplayPort, USB, Thunderbolt).
Thunderbolt 3 - connect Thunderbolt devices. Maybe USB 2.0. Not USB 3.x or DisplayPort (except the Apple Thunderbolt 3 Pro cable which is probably more like a Thunderbolt 4 cable https://support.apple.com/en-ca/HT210997 )
USB-C - (10 Gbps data cable) connect anything (but Thunderbolt only connects at 20 Gbps speed).

Thanks for this thorough breakdown. ??

It amazes me that the price difference varies so much. <$20 for USB-C, $40 for Thunderbolt 3, and as much as $150 for Thunderbolt 4!

 

[edanuff]

Thanks for this thorough breakdown. ??

It amazes me that the price difference varies so much. <$20 for USB-C, $40 for Thunderbolt 3, and as much as $150 for Thunderbolt 4!

It depends on the length, quality, certification, and whether these are active cables. People used to complain about Thunderbolt because of the perceived Apple tax that Apple or companies serving the Apple ecosystem charged. At this point, Thunderbolt is much more mainstream. The more expensive long cables have active electronics in them which is a big part of the cost of the cables that are over $75 or so. And if you have to go over 6 feet from your Mac to the Studio Display as I discovered when routing the cable through my monitor arm, you’re looking at even more expensive Thunderbolt optical cables until Apple finally releases its Thunderbolt 4 Pro cable. OTOH, if you have non-Thunderbolt hardware on either side of the connection - for example a Mac to a regular 4K monitor, you can find a relatively inexpensive cable but you need to read the descriptions carefully as to what it supports, specifically that it mentions DisplayPort or “DP Alt Mode”. If you don’t see those words, it’s not good for use with a monitor. Finally, if you’re using a 4K or greater display and it’s not Thunderbolt, then don’t expect your monitor’s USB hub to be very fast unless you’re using separate USB and DisplayPort cables, like you can on some Dell 4K monitors.

 

[joevt]

I split Thunderbolt 3 cables into two categories: active and passive #2 .
I can use a Thunderbolt 3 passive cable to connect a USB NVMe device at 1060 MB/s.

 

[BeatCrazy]

A handy guide from Akitio. It's missing TB4, but those can basically "do everything".

 

[snak-atak]

• Thunderbolt 3 (active cable - usually long) - connect Thunderbolt devices. Maybe USB 2.0. Not USB 3.x or DisplayPort (except the Apple Thunderbolt 3 Pro cable which is probably more like a Thunderbolt 4 cable https://support.apple.com/en-ca/HT210997 )

Thank you. I found this link very informative, especially the fact that the Apple charging cables only support up to 480MB transfer speeds. I’ve been accumulating cables from various purchases over the past couple years including Apple charging cables. I now know that I have to do a better job of labeling those cables so I use the right cable for the right job.

 

[snak-atak]

A handy guide from Akitio. It's missing TB4, but those can basically "do everything".
View attachment 1993584

This is an excellent illustration. I never could understand why some vendors sold .8m cables. Why not just sell 1m or 2m cables? Now I know why. I wish all the vendors would include them his illustration. It would make purchases that much more easier.

 

[joevt]

A handy guide from Akitio. It's missing TB4, but those can basically "do everything".

The chart is missing the fact that a 10 Gbps USB-C cable can do Thunderbolt at 20 Gbps (which is 10.3125 Gbps per line).
Also, a 10 Gbps USB-C cable can do DisplayPort at HBR3 link rate (8.1 Gbps per lane DisplayPort 1.3/1.4). Maybe the chart is pre-Titan Ridge (made during Alpine Ridge which only supported DisplayPort 1.2).
HBR2 is 5.4 Gbps (DisplayPort 1.2) which might be too much for a 5 Gbps cable? But if a 10 Gbps can do 10.3125 Gbps then may 5.4 Gbps isn't too far off from 5 Gbps? But the former is only a 3% increase while the latter is a 8% increase. I don't think I have any 5 Gbps cables to test.