I want to buy a multi-purpose USB-C cable that will allow me to both charge devices and transfer data. I have an iMac and I am guessing I need to buy a USB-C cable that is compatible with Thunderbolt speeds?
Thunderbolt 3 complicates things (not 100% sure about thunderbolt 4 though), despite all using the USB-C connector.
Thunderbolt 3 cables come in two types active and passive. Passive cables are short (0.5m) but are backwards compatible with USB. Active cables are longer (up to 2m and more expensive) but not compatible with USB (only thunderbolt).
I think Thunderbolt 4 (which is not the same thing as USB4) only has passive cables.
I am pretty sure they were trying to make things more complicated but had to rush the spec out the door before all the complications were implemented. /s
Intel donated the Thunderbolt 3 specification to USB some years ago, and the end result of extensive massaging of the Thunderbolt 3 technology is the new USB4 standard. Unlike Thunderbolt 3, USB4 was built from the ground up as a USB standard, meaning it has extensive design considerations for backward compatibility (all the way back to USB 1.0 devices).
I wrote a long explainer of where USB4 is different from Thunderbolt 3 here: https://www.reddit.com/r/UsbCHardware/comments/mjz2pu/usb4_architectural_explainer_usb4s_and/
Thunderbolt 4 is Intel’s specific implementation of USB4 and a set of requirements that basically turns on a bunch of optional bits in USB4 as mandatory in order to be called Thunderbolt 4.
A Thunderbolt 4 implementation should be a good USB4 implementation.
Cables is one area where the USB standards body took what Intel did wrong for Thunderbolt 3 and fixed it. Most Thunderbolt 3 active cables are heavily nerfed to basically only support TBT3 and not USB3.
Thunderbolt 4, because it is based on the far more backward-compatibility and forward-compatibility conscious USB4 standard, require that all cables support USB3.x as well, which requires some amount of protocol awareness inside the cable.
Thunderbolt4/USB4 Active cables exist today. The 2M version of Caldigit’s Thunderbolt 4/USB4 cable is active, and basically supports all existing protocols that can run between two USB-Cs:
This is as close to a do-everything cable as can exist today, until the next thing!
I think the “really good” ones are still expensive. You theoretically want one that is Intel certified (Thunderbolt is Intel’s to manage).
In my experience, CableMatters makes pretty good stuff. Very well found. That cable comes in $16 cheaper than the CalDigit one I linked to above. https://www.amazon.com/dp/B08NFQ32PR
Yes, if you find Intel Certified, it means Intel (or one of their proxies) has tested and signed off on the cable.
By the way, I took the liberty of buying this cable and comparing it with the Caldigit cable:
The two cables digitally identify themselves identically, down to the Vendor ID and Product ID.
Both are Active Thunderbolt 4/USB4 cables with backward compatibility with USB1.1/2.0, USB 3.x, DisplayPort Alternate Mode, and Thunderbolt 3.
They’re both sourced from the same cable maker, it seems, but the CableMatters one is priced lower.
And both much more expensive to buy in Canada sigh In the past I have considered acquiring one, to have around just in case, but the prices keep scaring me off when I don’t really yet have any need for one. My only real USB-C devices being a Pixel 2 XL phone or a Stadia controller. If I can ever get the parts and build my next PC, maybe it will be USB-4 by then and I want a reliable cable on hand just in case.
Yeah, I’d agree that in your case it would be best to wait and see and buy what you need when the rest of your hardware requires high bandwidth.
Active Cables are actually less future-proof than passive cables, since their complex electronics need to be precisely designed to handle a specific set of protocols (USB3, DisplayPort 1.2/1.3/1.4, Thunderbolt 3, USB4), and in a few years, if the industry introduces a newer or faster mode, the old active cables will likely work less well.
This is exactly what happened with Thunderbolt 3 active cables, and the small number of USB 3.2 active cables, which simply cannot be used to enter USB4 mode.
My advice: Just buy the cable you’ll need based on your current use case. If you don’t need high bandwidth, don’t sweat it until you do. The landscape could change in a year or two.