MacBook – use a Thunderbolt 3 cable in place of a USB-C cable

Given that the computer sleep seems to be the problem, I turned off the "Power Nap", and it seems to be working for me now.

• System Preferences > Energy Saver
• Power Adapter tab
• Uncheck "Enable Power Nap while plugged into a power adapter

This seems to be preventing the computer from sleeping and my external monitor has been fine. Note that I still turn off the display after 10 minutes, so I don't think this is harmful to the computer.

Of course, this setup is only when plugged in, which is the only time I care about the external monitor.

The "lightning" does not indicate that it can transmit power - it is actually the Thunderbolt logo indicating that it is a Thunderbolt cable.

All Thunderbolt 3 cables have USB-C connectors. Note that this is just the connector itself - it doesn't mean that the rest of the cable is the same.

Ordinary Thunderbolt 3 cables (i.e. cobber-based) also work as USB-C cables. In this manner they are compatible. You can buy optical Thunderbolt 3 cables (eg. if you want a 50 meter cable) - these are normally not usable as a USB-C cable.

On the other hand any USB-C cable is not Thunderbolt 3 compatible. It might be (as ordinary Thunderbolt 3 cables also work as USB-C cables). In general they are not.

The differences are mainly the design and quality of the cable, and to which standard they have been tested before leaving the factory. For example Thunderbolt 3-cables are generally specced to allow much higher amounts of power delivery than USB-C cables.