eGPU not running at full speed? Vega 64 Razer Core X iMac5K

Working in latest beta of Resolve Studio 16 and installed a Razer Core X eGPU with an RX VEGA 64 card on iMac 2017 5k running High Sierra 10.13.6.

Definite improvement particularly after grading etc and export speeds much better than stock internal card alone, BUT the Vega64 isn't running at max speed/capacity!

I tried exporting a sequence with both internal AND external GPU's and while the internal card showing it was at max performance, the Vega64 was only running about 50%!

Tried running with the Vega64 ONLY and it ran full pelt 100% and actually matched the performance of the render run using both cards, on its own!

So, I can't help feeling a little annoyed that when running both cards, that the Vega64 isn't pulling its weight.

Any way of 'forcing' the Vega64 to be the dominant card and do most of the work?

Here's the GPU history for that render run....

Screen Shot 2019-06-13 at 18.54.19.png (51.38 KiB) Viewed 2945 times

If you have two different GPU, the software will pair the performances to the lesser of the two.

Really? Kinda makes the decision to buy a Vega64 a big waste of time then. Is there really no way to get maximum performance out of this card? (other than use it solo).

Really? Kinda makes the decision to buy a Vega64 a big waste of time then. Is there really no way to get maximum performance out of this card? (other than use it solo).

Use the 580 for displaying only and use the Vega64 for the compute workload.

When 2 or more GPU's are used, Resolve tries to balance the load between them, hence the slowest will be the bottleneck. Not many (non to my knowledge) programs have a GPU task scheduler that can maximize the load on 2 (or more) different GPU's.

Really? Kinda makes the decision to buy a Vega64 a big waste of time then. Is there really no way to get maximum performance out of this card? (other than use it solo).

Use the 580 for displaying only and use the Vega64 for the compute workload.

When 2 or more GPU's are used, Resolve tries to balance the load between them, hence the slowest will be the bottleneck. Not many (non to my knowledge) programs have a GPU task scheduler that can maximize the load on 2 (or more) different GPU's.

Thanks. How do I specify which does what?

When 2 or more GPU's are used, Resolve tries to balance the load between them, hence the slowest will be the bottleneck. Not many (non to my knowledge) programs have a GPU task scheduler that can maximize the load on 2 (or more) different GPU's.

It is highly dependent on what the distributed work unit is. If it is a bucket in render engine it is not a problem to max out all gpus because order of buckets makes no difference. But in case of some inherent linearity, things get messy. While Resolve could distribute frames to gpus in random order and reorder them when received, format decoding and disk io can make this practically unreasonable. So in practice they probably feed the gpus in ordered manner and this makes slowest gpu the bottleneck.

Rumors are that Nuke 12 will involve a specific scheduler for mixed multi cpu-gpu environments, they have done r&d in Foundry in this area and I have seen one tech talk by Nuke engineer specifically about this scheduling. Can't find the link anymore unfortunately...

If you have two different GPU, the software will pair the performances to the lesser of the two.

two D700 (6gbx2) + Egpu Radeon Vega Frontier Edition (16gb) Thunderbolt2
workload : rendering 4K files from Sony FS7 + Resolve OFX Grain

Ok, so now I'm confused... Resolve can? or can't? use all GPU's at the same time or is that example because they are all same speed or RAM specs?

Ok, so now I'm confused... Resolve can? or can't? use all GPU's at the same time or is that example because they are all same speed or RAM specs?

D700 for display and Radeon VII for rendering (D700 get really hot when rendering).

Just check the Resolve manual how to set the GPU's (slowest for display, fastest for render).

Have checked the manual, but can't see instructions for specific tasks per GPU, certainly not one for timeline and one for render?

In the top menu: DaVinci Resolve > Preferences... > Memory and GPU (under the System tab). The settings under GPU Configuration are the ones you need to change.

In the top menu: DaVinci Resolve > Preferences... > Memory and GPU (under the System tab). The settings under GPU Configuration are the ones you need to change.

Thanks I'm aware of that menu but neither using manual (metal) or auto makes any difference to the Vega64 only running at 50% capacity.

The important thing is to uncheck "Use display GPU for compute". In that case you also shouldn't have any monitor connected to the Vega.

If that doesn't help I guess the thunderbolt bus is the bottleneck. Being an iMac I assume you can't disable the internal GPU, but normally you probably should to prevent the back-and-forth of the image data.

It really is pretty simple. Set the engine to Metal, GPU choice to manual, select Vega only. "use display GPU to compute" will be greyed out. Your 580 will just serve the display output, and Vega will do the heavy lifting.

You did not waste the money buying the eGPU. Davinci will perform much better in the above configuration than with both GPUs, or with 580 alone.

That being said, there are some tasks where you will never see a full load on the GPU. There are quite a few things in Davinci that are still reliant on CPU for the most part. Like, for instance, delivering in H.265, which is CPU-intensive process. Your activity monitor will show almost zero action on the GPU window, while the CPU will be maxed out.

Working in latest beta of Resolve Studio 16 and installed a Razer Core X eGPU with an RX VEGA 64 card on iMac 2017 5k running High Sierra 10.13.6.

Definite improvement particularly after grading etc and export speeds much better than stock internal card alone, BUT the Vega64 isn't running at max speed/capacity!

I tried exporting a sequence with both internal AND external GPU's and while the internal card showing it was at max performance, the Vega64 was only running about 50%!

Tried running with the Vega64 ONLY and it ran full pelt 100% and actually matched the performance of the render run using both cards, on its own!

So, I can't help feeling a little annoyed that when running both cards, that the Vega64 isn't pulling its weight.

Any way of 'forcing' the Vega64 to be the dominant card and do most of the work?

Here's the GPU history for that render run....

Screen Shot 2019-06-13 at 18.54.19.png

That's a brilliant explanation. Thanks for that! Will try it later.

Did it work in the end?

Cheers