Thunderbolt 3 speeds on M2 MBA

[Hammie]

So, I know the spec for TB3 of 40G max with guaranteed minimum 16G and TB4 supports 32GB minimum. I also know that TB3 reduces speed over 1m to 20GB max. Is this a cable restriction, or is the port "smart enough to know the distance. For example, if I use a 2m TB4 cable, on a MBA TB3 port, will I get 40G or 20G?

I was not able to find any clear information on this.

 

[jdb8167]

So, I know the spec for TB3 of 40G max with guaranteed minimum 16G and TB4 supports 32GB minimum. I also know that TB3 reduces speed over 1m to 20GB max. Is this a cable restriction, or is the port "smart enough to know the distance. For example, if I use a 2m TB4 cable, on a MBA TB3 port, will I get 40G or 20G?

I was not able to find any clear information on this.

The M2 MacBook Air can use Thunderbolt 3 data at 32 GB/s. This works on a short cable of around 0.5 m but longer cables need to have active electronics. Apple sells a $160 3 m cable that will give you all 32 GB/s of data. Longer cables that do not have active electronics are limited to 20 GB/s though I don't know how that breaks down for just data.

 

[ilikewhey]

its a cable restriction, thats why anything longer than the standard tb3 and tb4 cost an arm and a leg. i have the apple 1.8m tb4 that cost 130 usd, and on occasions where i do large file transfers, i was able to achieve the maximum output of the tb3 transfer rate.