Mac Pro 6,1 Thunderbolt Optimization

[cgscotto]

Hello,

I am trying to set up my Thunderbolt devices in the optimal configuration on my Mac Pro 6,1. Most research I have done suggests you not connect displays and storage on the same bus, which I have to do. Here are the devices I am connecting via Thunderbolt:

Dell U2718Q monitor
AOC HD monitor
Apogee Element 24 (audio interface-its speed is 10Gb/s)
2 UAD-2 Satellites (essentially external PCIe cards with DSP chips for audio processing-20 Gb/s)
OWC Drive Dock with two Samsung 2.5 SATA III SSDs (Thunderbolt connection to the computer-SATA III drive connector)

UAD says this about connecting Thunderbolt devices to the Mac Pro:

Thunderbolt port, and in most cases connecting six devices will not come close to exceeding the bandwidth of a Thunderbolt 2 bus - for example, up to four Thunderbolt Apollo interfaces and two UAD-2 Satellites could be daisy chained off of a single Thunderbolt port without exceeding the bandwidth of the Thunderbolt bus.

With that in mind, here is how I have my devices connected to the Mac Pro's three Thunderbolt busses:

Bus 1:
Port 1: Apogee Element 24
Port 2: 2 UAD-2s Daisy chained

Bus 2:
Port 1: Dell U2718Q
Port 2: empty

Bus 0
Port 1: OWC Drive Dock
HDMI Port: AOC monitor (resolution 1080p)

Based on the recommendation from UAD and what I have read about 4k monitors, I think busses 1 and 2 are optimally configured.

Since I have read that one should not place storage and displays on the same bus, my concern is Bus 0, which has the Drive Dock and the AOC monitor. I really don't see any other way to connect the AOC monitor and the Drive Dock, and I have not noticed any problems. Besides trying to optimally configure the Thunderbolt devices, my question is educational for me. That is, testing the idea whether storage and displays cannot share the same bus happily. Thanks for your thoughts.

 

[saulinpa]

The issue is more that you shouldn't place displays and storage on the same chain/physical port. You can only get 20gb/s through a single cable. I though the TB controller would let one physical port get the 4xPCIe while the other gets the displayport signals. It's not perfect but you do get better performance if DP is on one physical port and TB on the other using a single bus rather than plugging the DP in the end of the chain on one port.

Separately Bus 0's HDMI does not go through the TB controller so should have no affect.

 

[cgscotto]

The issue is more that you shouldn't place displays and storage on the same chain/physical port. You can only get 20gb/s through a single cable. I though the TB controller would let one physical port get the 4xPCIe while the other gets the displayport signals. It's not perfect but you do get better performance if DP is on one physical port and TB on the other using a single bus rather than plugging the DP in the end of the chain on one port.

Separately Bus 0's HDMI does not go through the TB controller so should have no effect.

Thanks, not putting a display and storage on the same cable (i.e., port) makes total sense. I can see how that might be an issue in a laptop with limited ports/busses. This also explains why the system profiler shows nothing connected to the Thunderbolt bus when a display is connected to one of its ports. The profiler shows the displays on their own PCIe lanes. I found this diagram of the PCIe lanes to the CPU, which basically confirms what you have said:

https://www.anandtech.com/show/7603/mac-pro-review-late-2013/8

I think then that I can redistribute the devices a little better. My main concern is when I had an RME Fireface audio interface, it needed its own Firewire bus. If anything was on the same bus, I would get audio dropout and glitches, and that was on a Mac Pro 5,1.

Thanks for confirming this.

 

[saulinpa]

Here is a snippet of how things are connected: