only 30% of gpu performance over expresscard slot?  

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(@christoph_mayrhofer)
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Joined: 9 months ago
Posts: 4
March 20, 2018 8:32 am  

I have a Lenovo T430s and use a GTX 770 via the expresscard slot. The passmark 3d benchmark only gives me a 1000-2000 score while I get 5000 - 6000 on my desktop with the GTX 770

Is this the expected performance? Would a thunderbolt Laptop get a much better ratio? 

I am trying to find out what the bandwidth of the expresscard slot is. Would it help to use the mPCIe connector inside the laptop instead?

I wanted to get rid of my desktop, but using a GTX 770 to only get 20-30 fps on my games seems very wasteful (I get > 70 fps on the desktop).

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nando4
(@nando4)
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Joined: 2 years ago
Posts: 1815
March 20, 2018 8:37 am  

Can see various eGPU interface bandwidths at https://egpu.io/build-guides/#perf including expresscard & mPCIe, plus others that offer more bandwidth. Also see here how to maximize performance on your expresscard link.

eGPU Setup 1.35    •    eGPU Port Bandwidth Reference Table    •    Several builds
2015 15" Dell Precision 7510 M1000M + macOS 10.14 & Win10


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(@christoph_mayrhofer)
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Joined: 9 months ago
Posts: 4
March 20, 2018 3:54 pm  

Thank you for the quick reply. I see that a GTX 770 is definitely overkill for an expresscard slot. They also just told me at the NVIDIA forum that the 770 would require pci 2 8x.

Does anyone have experience with different GPUs for pcie 2 1x? I am trying to find a gpu that can max out the bandwidth but without too much overhead (= wasted cost). 

Can someone tell me a good compromise?

Soon I will add my system & eGPU details or a build link to this my signature to give context to my posts


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Yukikaze
(@yukikaze)
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March 20, 2018 5:19 pm  

Are you running on an internal or an external monitor? Running on the internal off Expresscard is a very significant performance hit. Try with an external monitor. I used to run a HD7950 via Expresscard and it performed quite well.

Performance over Thunderbolt will be better, but I think you have some other problem on your hands: A GTX770 should not be bottlenecked by 70% via Expresscard.

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(@christoph_mayrhofer)
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March 21, 2018 10:47 am  

I am running on an external 1080p monitor. So far I have the following observations:

The CPU is not bottlenecking it (it's around 20-40%)

The 770 is very bottlenecked (~60% lower framerates)

An AMD HD 7870 has about 25% lower framerates

I will try an even lower card within the next few days to find the gpu level that is appropriate for pcie 2 x1

Does anyone else use an expresscard slot adapter? With which GPU? I would like to see if others also see such huge impacts with mid/high end cards.

Once we find the sweetspot the info could be put into the FAQs or a sticky so people don't waste money on overpowered GPUs that cannot be used with single lane pcie interfaces.

Soon I will add my system & eGPU details or a build link to this my signature to give context to my posts


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Yukikaze
(@yukikaze)
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March 21, 2018 8:15 pm  

You really should not getting a 60% bottleneck with a GTX770. Does your T430s have an NVidia NVS chip in it?

My eGPU Zoo - Link to my Implementations.
Want to output [email protected] out of an old system on the cheap? Read here.
"Always listen to experts. They'll tell you what can't be done, and why. Then do it."- Robert A. Heinlein, "Time Enough for Love."


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(@christoph_mayrhofer)
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March 22, 2018 8:18 am  

It does not have a dGPU, only HD4000

However, I could now see that the 60% is only in the passmark 3d benchmark
When I run unigine valley the drop is "only" from 50 to 38 fps (~25%)

The passmark results are really strange though:

Desktop: https://ibb.co/hV2q5H

eGPU:  https://ibb.co/dAm6ec

GPU Compute and DX11 are within the expected range, but DX9/10/12 have massive performance hits.

I also found out that the max supported framerate for Farcry 3 (ultra) seems to be around 30 fps. 
I could tell because on the desktop I get about 2x the framerate with 2D compared to enabling 3D vision.

With the eGPU they are almost the same (i.e. the framerate is 30 with 3D and does not get any higher even when I turn it off)
I guess this is because the GPU uses the same data that it gets from the CPU to render both images for 3D. It therefore requires

the same pcie bandwidth as 2D. And since the framerate does not increase when I disable 3D I am pretty sure that 30 fps is

the maximum that can be pushed over pcie single lane for this game/settings

Soon I will add my system & eGPU details or a build link to this my signature to give context to my posts


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