alt Hacker News> Actual maximum data throughput is very hard to know. The only way to really "know" how much data can flow through a cable is with an expensive oscilloscope or cable tester.
Couldn't you just do a data transfer test over the cable and check the error rate? At least in theory, the controller might not report enough I guess.
If you are just wanting "to use it", sure. If you are building a cable for a specific purpose, or want to actually ensure that it will work, use test equipment.
IT interconnect closet vs. air vehicle.