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Internal/External monitor usage on 2PCI lanes when not gaming?
 

Internal/External monitor usage on 2PCI lanes when not gaming?  

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blerghcity
(@blerghcity)
Eminent Member
Joined: 8 months ago
 

Hello there, 

I've been lurking this wonderful site and have finally worked up the courage to ask what is potentially a dumb question. 

I have a Matebook X Pro which while very nice, unfortunately only has 2 PCI express lanes on its thunderbolt 3 port. I'm looking to purchase an eGPU anyways though, to plug the Matebook in while gaming and have read all about the negative effects of having only 2 PCI lanes with an eGPU. But based on parsing through a bunch of posts on this and other sites it really seems to me that getting an eGPU will still be worth it even with 2 lanes, and while I may suffer a little worse performance than with 4 lanes, a good eGPU with a decent GTX or RX GPU will still give me much better performance than the onboard MX150 on the Matebook X Pro, as long as I only use an external display and not the matebook x pro's screen as well while docked.

I'm totally fine with that condition as I'd only use one external display when gaming anyways. My question I can't seem to find an answer for is this: would I be able to use both an external display hooked to the eGPU displayport and my Matebook's internal display simultaneously when doing less demanding tasks? Like just normal web browsing, working with microsoft office, stuff like that. Or would I still have poor performance?

My gut tells me it would be fine to go dual screen when not gaming but I don't know enough about this yet to know for sure, and I'd like to confirm before I pull the trigger on a pricey-yet-convenient one cable docking setup. Thanks in advance for any insights!

This topic was modified 8 months ago

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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Nicolaj
(@nicolaj)
Active Member
Joined: 10 months ago
 

Yes of course.

If it's nothing demanding the bandwidth shouldn't be an issue.

2018 15" Zenbook Pro 15 (UX550GE) GTX 1050 Ti + RTX2070@32Gbps-TB3 + Win10


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blerghcity
(@blerghcity)
Eminent Member
Joined: 8 months ago
 

Awesome! Thank you! 

I've had my eye on either an Aorus box or an Akitio Node Pro for Daisy chaining purposes. Time to go prowl for deals

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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itsage
(@itsage)
Famed Member Admin
Joined: 3 years ago
 

@blerghcity If you connect an eGPU, I’d recommend disable the MX150 dGPU (in Device Manager) so that the eGPU can fully take over. This will make sure the system use the eGPU for all tasks. The x2 PCIe lane limit on the Matebook X Pro is not ideal but for non-gaming tasks you should be alright.

Best ultrabooks for eGPU use

eGPU enclosure buying guide


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blerghcity
(@blerghcity)
Eminent Member
Joined: 8 months ago
 

@itsage thanks for the input! Would there be a way to have the MX150 disabled automatically every time I connect the eGPU, and auto-re-enabled every time I remove the thunderbolt cable? Or would something like that have to be done manually every time? 

Also, I ran HWiNFO64 on my system and saw it was using 4x lanes for the SSD, 4x for the MX150, 2x for the TB3, 1x for the wifi, and could not figure out where the 12th lane was dedicated to. On laptops like the Blade Stealth that have 4 lane TB3 ports, where else is making the sacrifice? Do the dGPUs only have 2 lanes, or do they have no dGPUs at all? I noticed the new blade stealths have versions with and without an MX150; do the ones with the MX150 still have 4-lane TB3 ports? I'm not seeing how you could have an NVME ssd, 4-lane MX150, 4-lane TB3 and still room for wifi and bluetooth. I thought you could only have 12 lanes total but maybe I was mistaken?

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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itsage
(@itsage)
Famed Member Admin
Joined: 3 years ago
 

I’m not aware of a script or software utility to disable/enable the dGPU automatically based on whether the eGPU is active. Maybe Intel can work on integrating such feature to its Thunderbolt software.

Regarding the PCI lane allocation to components, many sustems don’t use all the lanes available. You brought up a good example with the new 2019 Razer Blade Stealth. Razer switched to using a i7-8565U CPU vs. i7-8550U in the 2018 model. This i7-8565U processor has 16 lanes so it’s now possible for Razer to add a dGPU without crippling the Thunderbolt 3 controller and port with a x2 PCIe connection. This is the same approach Apple did with the 2018 13″ MacBook Pro to host two Thunderbolt 3 controllers and four ports.

Best ultrabooks for eGPU use

eGPU enclosure buying guide


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blerghcity
(@blerghcity)
Eminent Member
Joined: 8 months ago
 

Ah gotcha. Have you ever heard of an odd number of lanes being used (other than 1)? Like, since the Matebook X Pro seems to have one left over would it have been possible to give the TB3 port 3 lanes instead of 2? I've only ever heard of 1, 2 or 4.  And that's good info about more lanes in other models, I always wondered if 12 was the maximum in laptops. Thanks!

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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itsage
(@itsage)
Famed Member Admin
Joined: 3 years ago
 

The lane configuration options are x16, x8, x4, x2, and x1.

Best ultrabooks for eGPU use

eGPU enclosure buying guide


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bootz
(@bootz)
Eminent Member
Joined: 3 years ago
 
Posted by: blerghcity

Hello there, 

I've been lurking this wonderful site and have finally worked up the courage to ask what is potentially a dumb question. 

I have a Matebook X Pro which while very nice, unfortunately only has 2 PCI express lanes on its thunderbolt 3 port. I'm looking to purchase an eGPU anyways though, to plug the Matebook in while gaming and have read all about the negative effects of having only 2 PCI lanes with an eGPU. But based on parsing through a bunch of posts on this and other sites it really seems to me that getting an eGPU will still be worth it even with 2 lanes, and while I may suffer a little worse performance than with 4 lanes, a good eGPU with a decent GTX or RX GPU will still give me much better performance than the onboard MX150 on the Matebook X Pro, as long as I only use an external display and not the matebook x pro's screen as well while docked.

I'm totally fine with that condition as I'd only use one external display when gaming anyways. My question I can't seem to find an answer for is this: would I be able to use both an external display hooked to the eGPU displayport and my Matebook's internal display simultaneously when doing less demanding tasks? Like just normal web browsing, working with microsoft office, stuff like that. Or would I still have poor performance?

My gut tells me it would be fine to go dual screen when not gaming but I don't know enough about this yet to know for sure, and I'd like to confirm before I pull the trigger on a pricey-yet-convenient one cable docking setup. Thanks in advance for any insights!

From my understanding (and how my iMac TB2 works when using the internal display), the iGPU renders the image that is sent from the eGPU. The eGPU always has overhead when using the internal display, even if there is zero 3d activity.

For a real world scenario, if I'm running a 2d app, such as Google Chrome, via the eGPU, back to the internal display, the highest resolution that works at a solid 60 fps is 1440p. Anything higher and frames start dropping. At the 4k resolutions, the performance goes down to 24-30 fps. Even though I'm using a 2015 iMac, it is an i5 desktop CPU, so a laptop CPU may reduce the performance.

So the TL;DR: Light load eGPU tasks should be able to work with no comprimise in display output as long as you stick to 144op and below.

This post was modified 8 months ago

iMac 4k 2015 - 21.5" (iGPU only)
i5-5675R @ 3.10 GHz
8 GB RAM
Aorus Gaming Box 1070 via TB3 > TB2 adapter
Windows 10.0.17134


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OliverB
(@oliverb)
Noble Member
Joined: 12 months ago
 

The x2 Lane is ok as long you are using an external display and not going on very high FPS. I have done tests with the exactly the same chip, with x4 and x1 lane(s) at about 30 FPS and the result was almost the same. This changes a lot when accelerating onto an internal display though.

2018 15" MBP & 2015 13" MBP connected to RTX2080Ti GTX1080Ti GTX1080 Vega56 RX580 R9-290 GTX680


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