09-15-2017 06:30 AM
My company recently purchased a dual 4k setup for a work station. The setup is the following:
2 ThinkVision P27 monitors
Lenovo ThinkPad Thunderbolt 3 Dock
T570 (Type: 20HA)
I setup the monitors and docking station yesterday and was able to power the displays using a X1 Carbon 5th gen (i5 model type: 20HQ) thru USB-C without issue. I have a user testing out the desk now with a T570. I'm able to get one monitor to funtion at 4K and the other is running at 1080p. If you check display settings I'm unable to increase the resolution to 4K. I've updated all drivers on the T570 including the display driver and thunderbolt docking station driver this morning and the system still fails to power dual 4K. I brought back the X1 I used previously and it powers the screens normally. I checked the specs of the T570 and its identical to the X1 as far as processor is concerned and the model page claims the USB-C port on the T570 can power dual 4K. What else can I try?
10-21-2017 09:42 AM - edited 10-21-2017 09:44 AM
The X1 series have a full TB3 implementation with PCIe x4 and two DisplayPort lanes fed into Thunderbolt, while the x70 series use a crippled Alpine Ridge LP with half the bandwidth (PCIe x2 , one DP). I am surprised the second monitor works at all, if it does that means there's an MST hub there which then makes sense, 4K @ 60 takes 76% of the available DP bandwidth, 1080p @ 60 takes 22% so that works but even 1920x1200 @ 60 wouldn't (that's 30%).
10-23-2017 06:12 AM
10-23-2017 06:26 AM - edited 10-23-2017 06:27 AM
You are preaching to the choir, I already raised the false advertising claim at https://www.reddit.com/r/thinkpad/comments/73h86p/is_the_t470_falsely_advertised_thunderbolt_wise/ and if you lawyer the text then "up to 40 Gbps" is just that, "up to". Also, 4K doesn't mean 4K @ 60... you certainly can connect 4K @ 30 But "four times the data and twice the video bandwidth of any other port type" is much harder to defend. But: Lenovo.