MP 6,1 Adding TB3 to 2013 Mac Pro?

[Killerbob]

hmmmm - trying to add Thunderbolt 3 to my Mac Pro 2013...

I use a Sonnet Echo Express III-D external PCIe expansion box for a few storage cards, and I am upgrading my Echo Express to TB3 via a TB3 Upgrade card from Sonnet. This card replaces the TB2 card in the Echo Express and the new TB3 card has 2 x TB3 connections.

I will connect the Echo Express box and the Mac Pro using TB3 and an Apple TB3->TB2 adapter).

Hence, when connecting the Echo Express box with my Mac Pro, I will have one TB3 connection to spare.

Will this setup effectively give me a TB3 connection on my Mac Pro, albeit with a slower transfer rate, because it will still be limited by the TB2 connection between the Echo Express box and the Mac Pro?

 

[joevt]

Basically. The TB3 port works at TB2 speed. What you gain is a Thunderbolt/USB-C port that can connect USB-C devices (including USB 3.1 gen 2), USB-C displays, USB-C display adapters, Thunderbolt 3 devices and displays and display adapters (up to 20 Gbps).

There exist Thunderbolt 2 devices that will let you use USB controller PCIe cards that support USB 3.1 gen 2 - but Thunderbolt 2 is rare compared to Thunderbolt 3 and the PCIe cards don't have the USB-C display capability (unless the PCIe card is something like the Sunix UPD2018 but that requires a DisplayPort connection and it only supports 8 Gbps of data instead of 10 Gbps and will be limited to 4 Gbps of data while in a Thunderbolt 2 enclosure).

Since the TB3 port works at TB2 speed, you are limited to 20 Gbps of data and display bandwidth - which means you are limited to one 4K 60Hz display or two 1440p60 displays. A TB3 device can connect two displays while TB2 devices can only connect one display (in that case you need a second TB2 device to connect a second display). For example, you can now use a Thunderbolt 3 to Dual DisplayPort adapter to connect two 1440p 60Hz displays.