Any experiences with TB3 eGPU in Bootcamp with 2017 iMac?

Mac32

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Hi!

Has someone here used a Thunderbolt 3 eGPU in Bootcamp (Windows) with their 2017 iMac? How does it work? Say I use an Nvidia 1080 or 1080ti in a TB3 eGPU enclosure, how much performance will I loose compared to a similar internal GPU card - playing in 2650x1440? How big will the eGPU performance increase be compared to Radeon Pro 580?

PS: Does anyone also know when the successor to Radeon Pro 580 will be available, and what kind of performance increase we can expect?

PS2: How much performance gain in games can I expect by going from the 3.8ghz i5 to 4.2ghz i7 CPU?

Thanks!
 
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Precursor

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You'll lose about 10% performance on external display connected to the eGPU, 30% loss on internal display. Even with these losses, a GTX 1080 Ti eGPU will have higher fps than the Radeon Pro 580.

The successor to pro 580 will most probably be a modified (downclocked to decrease TDP) RX Vega which is already weaker than GTX 1080 Ti.
 
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Mac32

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Thanks! I guess the i7 makes little sense from a gaming perspective, as the Radeon Pro 580 has limited power (compared to Nvidia 1080ti and the like).
 

russofris

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Mar 20, 2012
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I have a Late 2012. I've been mulling over the same situation, and am a bit grief stricken with the cost of the outboard gear and the performance hit that comes along with it. My choices seem to be:

1: Wait for the next Vega/Coffee powered iMac, meaningful eGPU support, and price reductions.

2: Buy an iMac now, and build an mATX PC to leverage Nvidia Gamestream over thunderbolt networking.
 

Strelok

macrumors 65816
Jun 6, 2017
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It's PCI-E 4x vs 16x, so there are some losses but it's not too terrible. Using the internal screen is pretty bad though, as another user mentioned the performance drops can be quite drastic (30%). I would only use e-GPU's on NUC/Mini type PC's and laptops personally.

As for the i5 to i7 upgrade, I think it's worth it. That said, it seems the iMac's with i7's are much louder so it might not make sense in that situation.
 

Precursor

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Sep 29, 2015
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I didn't wait and went ahead and bought i7 iMac with Sonnet Breakaway Box with a GTX 1080 Ti 3 weeks ago. The eGPU box kinda makes it a little more future proof I guess, as I'll be able to replace the VGA card in it, but not completely as CPU is inside iMac and soldered. Still this iMac will last me at least 5-7 years. Mind you, everybody is saying the same thing about i7, but I've never even heard of the fan yet.
 

rjsounds

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Jul 3, 2017
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I have the i7 and I only hear the fan when rendering video, or extended periods of gaming. Otherwise the fan is ultra silent.

Also, when the fan does ramp up it's no problem for me because 1. I don't use the computer while it's rendering video and 2. The sound and music while gaming is usually far louder than the fan. Or put on some decent headphones and it isn't a bother.
 

Mac32

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Thanks for the replies. As far as i7, what I've seen is that hyper-threading makes the CPU considerably hotter (more than 10C). When gaming this could force the fan to run much louder, so i5 vs i7...it's a difficult call. I'm no expert, but I should think the GPU (and 2560x1440) itself limits the differences in framerates. The Radeon Pro 580 is only a midlevel GPU, and shouldn't give as big a difference vs. a high-end card like GTX1080ti for instance where more CPU overhead is needed. Dunno, maybe I'm wrong.

Right now I'm wondering if I should sit out for another generation of the iMac, and get the 2018 model and a slightly better GPU (give us back Nvidia options, Apple!). I think Radeon Pro 580 has a limited lifespan for decent framerates in 2560x1440.
 

fokmik

macrumors 68040
Oct 28, 2016
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if the next 27" iMac will have a Vega dGPU that is between Nvidia 1070 and 1080, it will be more than ok
 

rjsounds

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Jul 3, 2017
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Do you /need/ a new iMac now? I see you don't have a signature so I'm not sure what computer you currently have. If you can wait, it might be better to hold out because it's looking like the next refresh may end up with 6 core intel chips and even better gpus.
 

Mac32

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Yes, like russofris I have the fully-specced late 2012 model (SSD, i7 CPU, 680MX). I agree that the 2018 iMac model could be a serious upgrade worth waiting for. My biggest concern with the present iMac model is Radeon Pro 580 and gaming in 2560x1440, and once I buy such an expensive machine I need it to last for at least 4-5 years.

I'm a bit sceptical about the 6 core CPUs though, if this means lowering the CPU frequency. That way the performance could actually get slower for certain things. The single core performance increase from generation to generation in Intel CPUs are fairly small these days...