[Solved] XPS 15 - 9550 not able to reach 40Gbps over TB3?  

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AquaeAtrae
Eminent Member
Joined: 2 months  ago
Posts: 23
March 3, 2017 2:41 am  

Hi Marko,

Technically, even the x2 lane configuration does provide up to 40Gbps overall. It's not intuitive. Essentially, PCIe signals are just one of several that are sent within the overall Thunderbolt 3 cable. Most notably, there's also DisplayPort signals which use separate wiring and could utilize all the remaining Thunderbolt bandwidth.

Imagine two collapsible hoses within a larger, outer hose carrying up to 40 gallons of water per second. The inner PCIe hose needed for eGPUs can be connected to a larger x4 or smaller x2 faucet. The larger faucet could be opened to allow up to nearly 32 gallons per second while the smaller could open to almost 16 gallons per second. GPUs rarely need to open these faucets all the way and do their work just fine with just a trickle of water and an occasional gush coming through. Most of the hard work coming out of modern games is generated within the beastly GPU itself, just taking quick instructions from the CPU. But even in those rare instance that a faucet is fully opened, there remains space for DisplayPort signals too, with an overall maximum of 40 gallons per second possible regardless.

Thunderbolt 3 Technical Brief

So, Dell and other manufacturers really aren't misadvertising nor does fewer lanes prevent you from benefiting from a eGPU. There may be a few instances when having x4 lanes might expedite something within the graphics system, but overall the impact in actual games is small. You will still see FPS approaching those seen in a desktop system. Actually, you won't notice the half bandwidth until other technologies come along like super fast external RAID storage. Even the GTX 1080 simply doesn't use all that much still.

Edited: 3 weeks  ago

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Richard_Parker
New Member
Joined: 1 month  ago
Posts: 4
March 3, 2017 1:29 pm  

Thanks for posting Marko, I was about to email them about replacing the motherboard but you just confirmed what I anticipated they'd say. This is still such a let down as I was expecting this laptop to be future proofed for years. 


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slipperman62
New Member
Joined: 2 weeks  ago
Posts: 1
March 12, 2017 6:01 pm  

I'm new and I'm hoping to add to this thread. I just installed a new dell precision 7510 along with a razer core egpu and a nvidia gtx 1080 founders edition. While the the 7510 supports a 4x thunderbolt link and the cuda-z results look promising, the card otherwise doesn't work. Meaning even with the onboard nvidia m2000m disabled the other benchmarks don't seem to be using the gtx 1080 and must still be using the igpu (intel p580). Almost like the cuda cores are available to the system but the display isn't. Connecting an external display (dell p2715q) causes the local display to lock up in different ways. For example the cursor can move between screens but the system is otherwise locked up. Here the cuda-z and hwinfo results.

For some reason I can't upload the hwinfo results. Not sure why.


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nando4
Honorable Member
Joined: 4 months  ago
Posts: 530
March 13, 2017 1:50 am  
Posted by: slipperman62

 

While the the 7510 supports a 4x thunderbolt link and the cuda-z results look promising, the card otherwise doesn't work. Meaning even with the onboard nvidia m2000m disabled the other benchmarks don't seem to be using the gtx 1080 and must still be using the igpu (intel p580). Almost like the cuda cores are available to the system but the display isn't. Connecting an external display (dell p2715q) causes the local display to lock up in different ways. For example the cursor can move between screens but the system is otherwise locked up. Here the cuda-z and hwinfo results.

  

There is an existing Precision M7510 eGPU implementation at the following URL. Yes it has a x4 3.0 link to the TB controller.
https://egpu.io/forums/implementation-guides/dell-precision-7510-akitio-node-galax-gtx-1080-hof-its-working/

What's interesting is your CUDA-Z performance has double the host-to-device bandwidth shown in that link.This is worthy of an implementation guide as a M3510 too also had the same halve host-to-device bandwidth. You are getting full Tb3 performance proving the Precision M7510 (and likely M3510) have proper TB3 hardware implementations.

As to your question about driving the internal LCD,  the dGPU needs to be completely disabled to facilitate that. To do that go to Device Manager-> View Devices By Connection. Find your dGPU then directly above it will be a PCIe Port or Bridge. Right click to disable it along with which the dGPU will disappear. Reboot and test some apps to confirm eGPU acceleration.

Edited: 1 week  ago

DIY eGPU Setup 1.35DSDT override error 12 fixExternal GPU Buyers Guide: Top 2017 eGPU Enclosures compared


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