So i had an issue where my macbook was not connecting to my spectrum via thunderbolt unless my macbook was restarted. I bought the apple thunderbolt 4 cable to connect to my monitor but I decided to try a OWC small cable, and the OWC cable was able to connect, be unplugged, and reconnect to the mac. I figured apple made some wierd cable protocols and i decided to buy a razer cable bc it was braided n stuff, and strangely it had the same issue as the apple thunderbolt cable. Is the spectrum not able to connect w thunderbolt cables over 2m or is somehting else happening.
Before I get into the possible cause of this issue, I need to clear something up.
There are 2 different video standards that use cables with a USB type C connection: Thunderbolt display, and DisplayPort over USB alt mode. These are very different methods of carrying a video signal, and neither is compatible with the other.
The Spectrum only support DP over USB alt mode. This takes over some/most of the physical wiring in the USB-C cable to carry a DisplayPort signal rather than a USB signal. Most computers that are able to output Thunderbolt video are also able to output DP over alt mode.
This difference matters when it comes to cables. There is a maximum USB-C cable length that can passively transmit a video signal without it getting too much interference. That length is somewhere around 80cm to 1m for most USB-C cables, with only expensive Thunderbolt 4 cables going up to 2m.
To get beyond this limit, you have to use active cables. These cables have circuitry that boosts the signal so that interference causes less of a problem. The circuitry needs to understand the signal in able to boost it, and that’s where the problems come in.
It’s easy to find active USB-C cables that understand a basic USB signal, and Thunderbolt cables that understand both USB and Thunderbolt, but it’s uncommon to find cables that understand DP over alt mode. It’s been an optional part of the USB standard for a long time.
If you need a longer cable that works, you’ll probably need to get a USB 4 or Thunderbolt 4 cable. These will be very expensive (possibly USD $100 or more, even for a 3m cable) and even then there’s no absolute guarantee that it’ll work correctly.
This isn’t a Spectrum issue - it’s a USB issue. You can thank the USB-IF for making the spec confusing and having so much stuff that doesn’t need to be supported.
I understand the usb alt mode is a displayport 1.4 output with passthrough charging. I used the apple thunderbolt 4 cable which is 2 meters and it could not connect w/o restarting but i got charging. And I used razer 2 meter thunderbolt 4 cable and it had the same issue. I using a 0.3m OWC cable rn. I bought a 1m OWC and 2m OWC and I am goign to c if either works. ill post any updates but if anyones any 2m cables that works lmk.
Active cables were the problem. Something with the intel chip in the active cables was not connected from sleep or anything, that the passive ones dont have. I bought a 0.8 cable and it works perfectly.
2 Likes