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Graphics eGPU recent hardware comparisons

Discussion in 'Hardware' started by Pete J, 3 Dec 2018.

  1. Pete J

    Pete J RIP Teelzebub

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    Hey all,

    I've been trying to find a good review of various GPUs used as an eGPU. Long story short, I've got a 1080 Ti in mine and am wondering if owing to the Thunderbolt bandwidth issue, if that's the only GPU worth having until a new interface (Thunderbolt 4 etc) is released.

    The thing is, I value resolution over framerate - currently rocking a triple screen set up of 7960x1600. I'm finding this okay for a few games, but Star Citizen definitely suffers. The reviews I've managed to find focus on high framerate, 'low' resolution monitors and so hit CPU limits - annoyingly some don't seem to realise this.

    So, summing up: at what point does buying anything beyond a 1080 Ti for an eGPU set up running UHD/4K and above become pointless?
     
  2. David

    David RIP Tel

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    It's definitely a case of diminishing returns but, given the real lack of improvement in the RTX line-up in non-raytraced games, is there really any point in trying at the moment?

    I'm lucky that my setup meets my needs, almost perfectly, however your rather more extreme requirements are clearly pushing the bounds of the current tech.

    I think we're waiting for either TB4 or eGPU/Laptop setups that can make use of some sort of TB link aggregation, before we see further improvements.
     
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  3. sandys

    sandys Well-Known Member

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    Yup the focus on 1080p is a bit silly.

    If the data stays within your framebuffer would it thrash the bus if the data is going out on a big screen attached to eGPU, isn't the big performance issue when you have to process and send back to laptop display?

    I guess the only way you could make an educated guess would be to borrow a lower spec GPU and test on yours see if the reduction in performance correlates with a typical desktop machine to rule out PCIe bandwidth.

    If it is bandwidth then problem you have is Intel doesn't have a chip with an appropriately good architecture to support faster as TB comes off of the chipset and faces contention with everything else off of the chipset bus to CPU which is equiv to a 4x PCIe connection, so despite offering 24 lanes on the chipset, you aren't expected to use them for bandwidth, bit rubbish, there is no fix for that.

    Or just buy a desktop :p
     
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  4. edzieba

    edzieba Virtual Realist

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    They drop resolution to increase framerate precisely because it's framerate (i.e. the number of times per second the CPU has to talk to the GPU over the bus) that impacts PCIe link speed. If they tested at high resolution, all the tests would just say "PCIe link speed has practically no effect".

    Which I suppose is your answer: if you're running at high resolution, PCIe link speed has practically no effect.

    Framebuffers are pretty tiny, even at high resolutions. A UHD frame is 3840x2160x24 bits, or 23.7 Megabytes (compared to TB3's unidirectional 2.5 Gigabytes per second).
     
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  5. Pete J

    Pete J RIP Teelzebub

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    That's my thinking too. Until a new link technology comes along, I'm thinking that perhaps a 1080 is probably the most sensible choice cost/performance wise for eGPU in its current state.

    I'm glad you share my annoyance about the focus on 1080p! As you say, I've also read that using an eGPU to run the laptop display results in a large performance hit. I run mine with the laptop screen deactivated when docked, so t should be mostly one way traffic. I might see if I can buy and then return a card to see what difference it makes.If I do, you can bet I'll publish the results here.

    On another note, really glad I ditched the high power PC for the laptop/eGPU combination :p:. For some reason I find it a lot more reliable!

    I know for a fact that high resolution performance is still impacted. So your initial assumption is wrong (in my opinion). It would just be nice to know to what extent performance is impacted.

    Hmm. Suppose I'm going to have to do this the hard way. I wonder if I can get hold of a few GPUs to try.
     
  6. faugusztin

    faugusztin I *am* the guy with two left hands

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    AFAIK the bandwidth limit is making anything above RX590/GTX1060 useless. And sending it back via same cable makes the situation even worse.
    Just look at the review here: https://arstechnica.com/gadgets/2017/08/laptop-external-graphics-card-review/2/

    For example Rise of the Tomb Raider - RX580 has 51 FPS average vs 83 with 1080 Ti on internal display. 54 vs 102 on external display. That is compared to 77 and 169 FPS respectively with the cards in a 7700K system.
     
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  7. David

    David RIP Tel

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    I don't see the point in using the eGPU to accelerate performance on the laptop screen. Mine is a glorified laptop dock, giving me decent gaming performance when required without having a laptop that wails like a banshee.

    But then, I viewed the eGPU option as a compromise - I have a great laptop with basic gaming chops that serves as a very quiet, yet reasonably potent desktop replacement when hooked up to my mouse, keyboard and monitor via the eGPU box.

    Given Pete's hardware history, I was very much surprised he chose an eGPU - no currently available setup could begin to match the performance he is used to - but I understand the desire.
     
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  8. bawjaws

    bawjaws Well-Known Member

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    Yeah, I agree with this. If you're hooking up a laptop to an external, mains-powered box, why not go the whole hog and use an external monitor too. That's even before factoring in that using the laptop screen means a performance hit (because you're asking the interface between eGPU and laptop to carry data both ways). Just my 2p of course.
     
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  9. Pete J

    Pete J RIP Teelzebub

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    Ahh, sod it, I'll give you a brief history of how I've ended up with the set up. Long story short, I gave up on gaming but got back into photography. I've sold my main PC and I looked into selling my screens, but the final auction price on eBay was way too low so I reneged. I had also bought an XPS13 as I wanted a nice travelling laptop. Using an eGPU allowed me to use the screens to do photo editing, then I realised I could still use it to surround game. I still have my Titan Xps in my lounge rig for seriosu 4K gaming though.

    Having experienced how fluid it is to use an eGPU, I'd now fully recommend it as a standard set up for anyone who uses their PC for pretty typical usage. Only those who want every last ounce of performance for high frame rate gaming or are doing a shed load of content creation/number crunching. Bring on the eGPU revolution!
    Could not agree more.

    I wonder if having the laptop screen as the secondary monitor while the external monitor is the primary also influences performance - as mentioned, I deactivate the laptop screen when connected to the eGPU.
     

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