eGPU Performance Loss - PCI Express vs. Thunderbolt
 
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eGPU Performance Loss - PCI Express vs. Thunderbolt  

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ataylor
(@ataylor)
Eminent Member
Joined: 2 years ago
 

I as more wondering how NOT having the monitors connected to the egpu's but directly internal via tb3 adaptor will effect things. i.e will i not get full speed out of the gtx cards when no monitor is connected to them? I assume it won't make a difference for "compute" tasks.

This post was modified 1 year ago

2018 MacBookPro 15 in. /w Touchbar - i9 - 32gig ram - 1080 Aorus 1080 Gaming Box - Sonnet-Breakaway550 with GTX 1080 - Still need to get both of the GTX 980TI working for 4 GTX total cards


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Martin Poon
(@martin_poon)
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Joined: 12 months ago
 

planned to get the Razer core x with RTX 2080ti, but hesitated after reading an article which said there is much 31% performance drop than those desktop setups

is it a hardware problem or software or alleviated any in recently?

IMG 8808

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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Rydell Hall
(@rydell_hall)
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Joined: 9 months ago
 

Am I understanding this right, if you have a Thunderbolt 3 laptop (we'll say the latest Razer 15" so everything is up to spec) with an eGPU connected to an external 4k monitor, you will only see a ~5% reduction in performance vs a similarly spec'd desktop? I started considering getting a laptop+eGPU to replace my desktop but saw specs that you lose up to 30% of the GPUs performance.  So now I'm reading this saying that's only the case for resolutions lower than 4k. I have a 4k external monitor that I would be using at home for gaming, then when I'm gaming away from home I'd just use my laptop by itself. This seems like the perfect solution if that's the case. I don't care about a 5% performance loss, but a 30% is not worth it.

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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Mini i5
(@mini-i5)
Honorable Member
Joined: 1 year ago
 

@rydell_hall

Until you personally test a specific game on a specific laptop+eGPU - and are able to adjust the relevant power and performance settings - go ahead and assume a 30% performance loss. 👨‍💻

Sometimes the loss will be greater, depending on the game, and the laptop’s thermal management (aka thermal throttling).

This thread is a good resource. It explains the various factors involved. There are many.

2018 Mac Mini i5 / 6-core 3.0-4.1 Ghz / 32GB / 256GB / Intel UHD 630 / PowerColor Gaming Station / PowerColor dual-fan RX 5700 XT / Mac OS 10.15.6 Catalina / Windows 2004 😏 / Dual LG 27" 4K displays


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Rydell Hall
(@rydell_hall)
New Member
Joined: 9 months ago
 
Posted by: @mini-i5

@rydell_hall

Until you personally test a specific game on a specific laptop+eGPU - and are able to adjust the relevant power and performance settings - go ahead and assume a 30% performance loss. 👨‍💻

Sometimes the loss will be greater, depending on the game, and the laptop’s thermal management (aka thermal throttling).

This thread is a good resource. It explains the various factors involved. There are many.

Appreciate the info. I read through the thread once again and it is seeming dicey. I'm about to pick up this laptop:

https://www.amazon.com/dp/B07HPQPNV1/ref=cm_sw_r_cp_api_i_pr4kEbYXJP4J6

With this card:

https://www.amazon.com/dp/B07HY6QWXN/ref=cm_sw_r_cp_api_i_It4kEb15JFN81

The goal is RDR2 on ultra (4k reso) with my existing 4k monitor w/ <10% performance loss

Seems what I'll have to do is start asking around if anyone has tried it with this specific setup. 

This post was modified 9 months ago

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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ron5553792
(@ron5553792)
New Member
Joined: 2 months ago
 

@enjoy, these are great comparisons, however I am left wondering impact of the CPU on these setup.

The experiment I would have liked to run is different combinations of:

1) CPU (4-8, 6-6, 6-12, 8-8, 8-16 variants of cores-threads, probably ignore overclocking for now)

2) GPU (980ti, 1660s, 1070, 1080, 1080ti, 2080 - not sure I would bother going higher or lower)

3) connection type (PCIe, TB3, TB2 - not sure I would bother with TB1 anymore)

That would be 5 x 6 x 3 = 90 combinations, of which many are covered here but not all (missing the CPU variable). I am also ignoring the internal monitor case - I would only ever use an eGPU with an external monitor.

My hypothesis is that:

A) The bottleneck can be CPU, GPU, or connection type depending on the specific combo, but CPU likely bottlenecking more often than connection type or GPU. 

B) If you already have a laptop, then your CPU + connection will be fixed, but there will be a "maximum" GPU for you to buy, ie. going beyond that GPU will result in higher and higher degradation compared to using that same GPU in a desktop, so it's not really worth it unless you can buy it for less than this "maximum" GPU. For example, if you have a 2-lane 8th gen Intel chip, then maybe getting a 1660 Super is the best you can do, because getting a 3090 will result in only marginally better performance at much higher cost.

C) if you already have a GPU, then there is a "minimum" CPU-connection combo when buying a laptop to pair with it, ie. maybe TB2 with 6 cores + 6 threads, or TB3 with 8 cores and 16 threads. For example, if you already have a 1660 Super, maybe you should hunt for a 2-lane 8th gen Intel chip (or better), while for a 1080, you need 4-lane 10th gen (or better).

One proxy for this experiment (which would take a lot of parts and a lot of time) is to see how your GPU does in "https://gpu.userbenchmark.com/".  My Titan XP for example scores over 100% on my desktop and only 15% on my EGPU setup. What is the highest % anyone has ever gotten on their GPU when running an EGPU setup?  This could also answer the question.

 

 

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