13" 2017 i7 TB Bandwidth

[Gudd]

With the release of the 2018 models I guess it's not the best of times to get a response on this!

SO, I know that on my MBP (2017 13" TB) the left hand TB3 ports have twice the throughput as the right hand ports so eGPU should be plugged into the left side for best performance.

Is the bandwidth shared between the two ports on the left in any way? For example, if I have an eGPU plugged into the rear left TB3 port and I then plug a TB3 dock or maybe TB3 hard drive in to the other left hand port, will it take bandwidth away from the eGPU or are both ports entirely independent?

 

[Closingracer]

With the release of the 2018 models I guess it's not the best of times to get a response on this!

SO, I know that on my MBP (2017 13" TB) the left hand TB3 ports have twice the throughput as the right hand ports so eGPU should be plugged into the left side for best performance.

Is the bandwidth shared between the two ports on the left in any way? For example, if I have an eGPU plugged into the rear left TB3 port and I then plug a TB3 dock or maybe TB3 hard drive in to the other left hand port, will it take bandwidth away from the eGPU or are both ports entirely independent?

Don’t think so. At least from what I understand.

 

[Gudd]

Don't think so which? That the ports are shared or that the ports are entirely independent? My bad, reading through I guess I managed to put two contradicting questions in the same paragraph

 

[curmudgeonette]

Is the bandwidth shared between the two ports on the left in any way?

Bandwidth between two ports on the same side is definitely shared! The two ports are both hooked to the same chip - which has one PCIe*4 connection to the CPU.

 

[Gudd]

Ahh, OK understood - thank you.

If at all possible then I should do my best to connect anything else that might be demanding to the right side and just suck up the fact it won't have the full PCIE lanes available. If for example it's a USB 3.1 drive it should be fine on the lower bandwidth of the right hand side anyway and then won't impact on the left hand side.

 

[Brookzy]

Each side has one Alpine Ridge Thunderbolt 3 controller (2016 and 2017 models), or one Titan Ridge Thunderbolt 3 controller (2018 models), so two controllers in total on all Touch Bar models.

The right hand side chip was crippled on the 2016 and 2017 13" models due to a lack of available PCIe lanes, but on the 2018 models this limitation is gone, as mentioned above.

But in all cases, the two ports on each side share a single controller, so in theory if you wanted absolutely peak performance you would try to balance the connections between the two sides, e.g. if you had two eGPUs, connect one to each side.

In practice this won't really be an issue though... a Thunderbolt 3 hard drive + an eGPU on the same controller still would not saturate the connection.