Why 2 Video Cards

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Nick Kurucsev

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Why 2 Video Cards

PostThu May 25, 2017 6:23 am

Hi,

I've seen a lot of posts on this forum with people using a Quadro card for GUI and a GTX card for rendering, I am curious as to the advantage of using the Quadro as GUI compared to just using the GTX and is there many issues with conflicting drivers between the 2. I am setting them up in a Lenovo p910 workstation.

Thanks in advance,
Nick
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Rohit Gupta

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Re: Why 2 Video Cards

PostThu May 25, 2017 12:12 pm

With Resolve 14, its best you go with a single GPU which is used for both UI and compute. It will give you better performance than a GUI + Compute card generally.

Only exception being if you have multi GPU system (for example 4), it might be better to have a GUI card for display and 4 dedicated cards for compute.
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Jake Melon

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Re: Why 2 Video Cards

PostThu May 25, 2017 12:29 pm

Good question, I was just about to add a 4gb card just for GUI in addition to my WX 7100 but there is no need.

thanks!
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Tony Martin

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Re: Why 2 Video Cards

PostThu May 25, 2017 1:04 pm

"With Resolve 14, its best you go with a single GPU which is used for both UI and compute.
It will give you better performance than a GUI + Compute card generally."

In what circumstance does "generally" apply?

I have been using two cards with version 12.

Do you advise that I go to the trouble of removing one and moving the better card (GTX 1080 Ti) to the main slot? Then the GUI display monitors would be attached to it which, in your previous guidance, should not be attached to the better of the two cards.

This is a surprising "gotcha" with version 14!

Guidance appreciated, please!
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Rohit Gupta

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Re: Why 2 Video Cards

PostThu May 25, 2017 1:11 pm

Tony Martin wrote:"With Resolve 14, its best you go with a single GPU which is used for both UI and compute.
It will give you better performance than a GUI + Compute card generally."

In what circumstance does "generally" apply?

I have been using two cards with version 12.

Do you advise that I go to the trouble of removing one and moving the better card (GTX 1080 Ti) to the main slot? Then the GUI display monitors would be attached to it which, in your previous guidance, should not be attached to the better of the two cards.

This is a surprising "gotcha" with version 14!

Guidance appreciated, please!


Resolve 14 has a whole new render engine and hence the recommendation.
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Ellory Yu

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Re: Why 2 Video Cards

PostThu May 25, 2017 3:07 pm

Sounds ridiculous to go back to a single GPU system after I spend on a second GPU a couple of months ago because I was told that Resolve works best with additional compute GPU and to separate it from the display GPU.
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Tony Martin

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Re: Why 2 Video Cards

PostThu May 25, 2017 4:11 pm

"Resolve 14 has a whole new render engine and hence the recommendation."

Are you sure it is the best way?

As a quick test, I added two nodes of heavy noise reduction and one node of severe sharpening.

The Nvidia GPU Utilization utility shows this:

- my GUI GPU (GT 740) running at mostly 30-40% and peaking at around 50% utilization.
- my Compute GPU (GTX 1080 Ti) running at 70-80% and peaking at around 80%.

So I seem to be getting >100% which is more than I could get with one GPU.

Am I missing something?
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Jack Fairley

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Re: Why 2 Video Cards

PostThu May 25, 2017 6:33 pm

Tony Martin wrote:"Resolve 14 has a whole new render engine and hence the recommendation."

Are you sure it is the best way?

As a quick test, I added two nodes of heavy noise reduction and one node of severe sharpening.

The Nvidia GPU Utilization utility shows this:

- my GUI GPU (GT 740) running at mostly 30-40% and peaking at around 50% utilization.
- my Compute GPU (GTX 1080 Ti) running at 70-80% and peaking at around 80%.

So I seem to be getting >100% which is more than I could get with one GPU.

Am I missing something?


Yeah, 30-40% on your 740 would not be 30-40% on your 1080 Ti, which has almost 10x the memory speed and 10x the CUDA cores, and has a base clock almost twice fast on a newer and better architecture.
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Hendrik Proosa

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Re: Why 2 Video Cards

PostThu May 25, 2017 6:57 pm

Resolve 14 has a whole new render engine and hence the recommendation.


So having a gui+compute card only is better than having also an additional compute card or one card for gui and another for compute? I have a hard time understanding the logic of this from the perspective of writing a new render engine. Sounds like something really funky going on there if having an additional compute card would stall the whole system.
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Kel Philm

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Re: Why 2 Video Cards

PostThu May 25, 2017 7:27 pm

Ellory Yu wrote:Sounds ridiculous to go back to a single GPU system after I spend on a second GPU a couple of months ago because I was told that Resolve works best with additional compute GPU and to separate it from the display GPU.


Its probably it still is a better option for 12.5 just not for 14. BM have clearly improved efficiencies under the hood which prob now means the overheads involved with a seperate GUI card are greater than the benefits. Bottom line is that its faster which is good news.
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Larry Li

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Re: Why 2 Video Cards

PostFri May 26, 2017 7:22 am

I am having GTX970 for computation and Quadro M2000 for GUI now.

will it be better for me to take out the M2000 and only run the computer with GTX970, monitor attached to it and computation all in it?
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Christian Horne

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Re: Why 2 Video Cards

PostFri May 26, 2017 2:10 pm

viewtopic.php?f=21&t=59406&p=341565&hilit=1080ti#p341565

I was told to use just one powerful GPU as DR14 makes better use of single use GPU in a 16x slot and because these days with the newer cards running the displays on a separate GPU is no longer beneficial. If you had two GPUs of the same make and spec and have a MOBO that supports 2 X16 slots than maybe you would see a small benefit, but really DR14 has been rewritten at the core and makes better use of CUDA just as a modern program should. The next step I suppose would be for BMD to look seriously into open CL support as there maybe another Nvidia/AMD war on the horizon.
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Tony Martin

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Re: Why 2 Video Cards

PostFri May 26, 2017 3:27 pm

"The Nvidia GPU Utilization utility shows this:
- my GUI GPU (GT 740) running at mostly 30-40% and peaking at around 50% utilization.
- my Compute GPU (GTX 1080 Ti) running at 70-80% and peaking at around 80%."

I would be grateful if someone could explain to me why these results do NOT demonstrate that I would be better staying with my current setup rather than going to the trouble of reducing my system to a single 1080 Ti specifically for Resolve 14.

I do not have sufficient technical knowledge to come to a conclusion myself unaided.
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Christian Horne

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Re: Why 2 Video Cards

PostFri May 26, 2017 3:40 pm

Tony Martin

Is that when you are colour grading or rendering?
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Tony Martin

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Re: Why 2 Video Cards

PostFri May 26, 2017 4:18 pm

Christian Horne wrote:Tony Martin

Is that when you are colour grading or rendering?


I tested in the Color tab with two nodes of heavy NR and one node of severe sharpening and just watched the Nvidia utilization graphs. I tested on a 5 minutes long clip.
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Christian Horne

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Re: Why 2 Video Cards

PostFri May 26, 2017 4:23 pm

If you can try a rendering test and see which set up is best, DR now runs in performance mode and using the full 32bpc at the rendering stage, this may be where you will see a performance increase when using the one card in a 16x slot on the MOBO
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Tony Martin

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Re: Why 2 Video Cards

PostFri May 26, 2017 4:32 pm

Christian Horne wrote:If you can try a rendering test and see which set up is best, DR now runs in performance mode and using the full 32bpc at the rendering stage, this may be where you will see a performance increase when using the one card in a 16x slot on the MOBO


But to do that I would have to remove a card and re-configure the machine which is not something I want to do at the moment.

But thank you for that and if I do take out the card I will test on both grading and rendering - I hadn't thought of that.
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Christian Horne

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Re: Why 2 Video Cards

PostFri May 26, 2017 4:47 pm

If you search and download "Desktop Restore" it will allow you to save your desktop icons in there current place, pull the lesser card out of your system and make sure you 1080ti or what ever card is the most powerful into the top lane on the MOBO (X16) and plug your monitor or monitors into it and restart your system, if your desktop icons have moved right click and select 'Restore Desktop' and all the icons will resume there previous positions. This whole exercise takes about 5 mins to do, worth it for piece of mind, but remember in the World of computers nothing works as expected, lots of Voodoo and magic at play as two identical same spec machines never run the same :D
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Dermot Shane

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Re: Why 2 Video Cards

PostFri May 26, 2017 7:24 pm

Rohit Gupta wrote:With Resolve 14, its best you go with a single GPU which is used for both UI and compute. It will give you better performance than a GUI + Compute card generally.

Only exception being if you have multi GPU system (for example 4), it might be better to have a GUI card for display and 4 dedicated cards for compute.


Rohit;
is this also valid for dual proc machines with enough x16 lanes? ie; a z840 with dual 26xx's for example?

would it run just as fast with a single 1080ti as would with dual 1080Tis'?
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Rohit Gupta

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Re: Why 2 Video Cards

PostFri May 26, 2017 9:41 pm

Dermot Shane wrote:
Rohit Gupta wrote:With Resolve 14, its best you go with a single GPU which is used for both UI and compute. It will give you better performance than a GUI + Compute card generally.

Only exception being if you have multi GPU system (for example 4), it might be better to have a GUI card for display and 4 dedicated cards for compute.


Rohit;
is this also valid for dual proc machines with enough x16 lanes? ie; a z840 with dual 26xx's for example?

would it run just as fast with a single 1080ti as would with dual 1080Tis'?


The suggestion was only for systems with a less capable card for GUI and another for compute. If you have two high end cards, use them both for compute, and also use one of them for GUI. This is what happens on the 2013 Mac Pro for example. Remember to go and configure the GPUs manually in Preferences as by default Resolve will exclude the GUI card for compute.
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Pete Lightowler

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Re: Why 2 Video Cards

PostSat May 27, 2017 2:26 am

Rohan, are you saying that Resolve 14 will perform better with one single GPU versus 2 smaller GPU's?
I am about to embark on a 10 core Windows 10 PC and am really undecided on what GPU to purchase.
I was leading down the path of a single Quadro P6000 24gb card but was then steered towards two Titan XP's instead.
What are your thoughts on using a single large card versus a double Titan setup?
Would resolve 14 make full use of a single 24gb quadro card?
Could you advise on what is the best solution for Resolve 14 please?
Cheers Pete.
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Dermot Shane

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Re: Why 2 Video Cards

PostSat May 27, 2017 2:49 pm

The suggestion was only for systems with a less capable card for GUI and another for compute. If you have two high end cards, use them both for compute, and also use one of them for GUI.


Thank you for the clairifaction
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Adam Archer

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Why 2 Video Cards

PostSun May 28, 2017 8:34 am

I think there are some large generalisations in recommendations on this thread as well as a lack of clarity.

I think the suggestion is that if you have a powerful computational GPU and a less powerful "does the job" GUI GPU then you're better off with just the one GPU. One limitation of Resolve has been that it will only see the amount of RAM from the GPU with the smallest RAM. So you could have a P6000 with 24GB RAM as a computational GPU but if your GUI GPU only had 2GB then Resolve would see both as having 2GB.

If you have multiple x16 slots then there is definitely a benefit to multiple GPUs. There is no benefit to having a lesser GPU for GUI though so just use one of your cards for GUI. Depending on what media you're working with, there generally is only benefit to multi GPU if you have the CPU cores to feed them and you need to debayer your source media.

There really is no one simple correct answer on this. But let's say budget machines would get better bang for buck having one good GPU to do everything. Mid range machines would best have a CPU with a decent core count with a couple of decent GPUs, one being used for both GUI & compute. A high end system would be multi CPUs with high core count and multiple GPUs on a top end MoBo & System that can support it all.


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Uli Plank

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Re: Why 2 Video Cards

PostSun May 28, 2017 12:53 pm

Does Resolve really limit VRAM to the GUI GPU if you don't activate "Use Display GPU For Compute"?

Anyway, when I combined a lowly GT120 for GUI with a Titan-X the advantage of having that separate GUI card vs the Titan-X doing all the work was negligible.
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Adam Archer

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Re: Why 2 Video Cards

PostSun May 28, 2017 9:39 pm

Uli Plank wrote:Does Resolve really limit VRAM to the GUI GPU if you don't activate "Use Display GPU For Compute"?

Anyway, when I combined a lowly GT120 for GUI with a Titan-X the advantage of having that separate GUI card vs the Titan-X doing all the work was negligible.


Everything I have heard says yes, Resolve will limit the VRAM it uses to that of the smallest GPU, even if it is a GUI only GPU. Happy to be corrected by someone from Blackmagic if I am wrong on this, but I heard that directly from 2 different resellers so I'm fairly confident this is the case.
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Re: Why 2 Video Cards

PostMon May 29, 2017 12:23 am

Yes, but FWIU this an NVidia limitation, not one imposed by Resolve per se.
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Peter Chamberlain

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Re: Why 2 Video Cards

PostMon May 29, 2017 1:04 am

There continues to be miss information about the use of GPU ram in Resolve.

As previously explained, each GPU is treated as a separate item, so the ram in one GPU has no relationship to another. The GPU ram size defines the image size and processing that can be achieved before "running out of GPU memory"

Each GPU processes images at its full speed and so if you have one fast GPU and one slow the fast one will finish its calculations first... and wait idle for the slow guy.

So, if you have one fast and one very slow GPU, with v14 it's likely better to remove the very slow GPU.

If you have two fast, similar fast, GPUs, with v14 use both for compute even if one is also used for GUI.

If you have three or more GPUs, with v14 use the same GPU and if not at least very similar ram and core count from the same family of GPUs.

There are always exceptions to the guidelines but for now use this as your v14 guide.
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Adam Archer

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Re: Why 2 Video Cards

PostMon May 29, 2017 7:41 am

Thank you for the clarification Peter. Much appreciated


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Pete Lightowler

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Re: Why 2 Video Cards

PostMon May 29, 2017 8:30 am

Thanks for the clarification Peter. I understand things a lot better now.
Time to go shopping for some GPU's :)
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Tony Martin

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Re: Why 2 Video Cards

PostMon May 29, 2017 10:24 am

Rohit Gupta wrote:
Resolve 14 has a whole new render engine and hence the recommendation.


When you say "new render engine" are you referring to a new process for rendering out the footage from the render page?

Or are you using it in the looser sense of Resolve's processing of all its operations including e.g. grading?
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Peter Chamberlain

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Re: Why 2 Video Cards

PostTue May 30, 2017 1:07 am

Generic. In v14 it's significantly updated.

All image processing operations are rendering, sometimes to a disk but in non write to disk playback you are calculating the image, i.e. Rendering, to monitors. That's one reason you can be confident that what you see in the grading monitor is what is being sent to the file compression codec, assuming you are using one to disk.
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RobSmith

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Re: Why 2 Video Cards

PostTue May 30, 2017 6:51 am

Hi Peter,

Could you please explain the 3 GPU's-or-more setup? I have a standard ATI 5770 in a MacPro with 2 x 980ti in a Cubix box, are you saying V14 will be slowed down by the ATI 5770 now. Should I replace the ATI for another 980ti?

Cheers
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Re: Why 2 Video Cards

PostTue May 30, 2017 9:12 am

I'm going to upgrade my MacPro 5.1 & looking for best solution / combination.

Now I have:
Mac Pro (Mid 2010)
2 x 3,46 GHz 6-Core Intel Xeon X5690
48 Gb 1333 MHz DDR3
MacOS 10.12.5 system on SATA 512 SSD
4TB RAID0 for Storage & Cache
GUI GPU - ATI Radeon HD 5770 1024 МБ
Compute GPU - GTX 980Ti 6Gb

(I need USB3/USBC PCIe card to be installed - so I need more PCIe slots)

I have two ways -

1) sell my GTX 980Ti, buy one GTX 1080Ti 11GB and remove ATI Radeon HD 5770 GUI card from my system. (Sometimes I have to use it when updating the system).

2) do not sell my used GTX 980Ti but buy Single Slot GALAX GEFORCE® GTX 1070 KATANA 8GB to replace my old double slot GUI ATI Radeon HD 5770.

In my experience - even in DR14 - working on single 980Ti with 2 connected 2560*1440 displays and 4K-6K footage + Temporal NR (in 1080p project) gives me less Fps (and no realtime) instead of working with additional GUI ATI Radeon HD 5770 GPU.

All the more so - with single 980Ti i much more often see GPU memory full varning, while using 3 frames NR and delivering with "render at source resolution» option - I think this is because GUI requires large part of my 6gb memory.

How two cards with different GPU RAM (6 + 8 GB) will work together?
Does GTX 1070 KATANA 8GB will be limited to amount of 6GB like 980Ti only in DR - so 2GB will be freely used by GUI?
In future i want to upgrade my 980Ti 6gb to 1080Ti 11gb - will 8Gb 1070 Katana be the «bottleneck» for 11gb 1080Ti?

Both ways are approximately equal in price for me.

Tell me please - what is the better way to upgrade & what combination - GTX 1080Ti only vs GTX 980Ti + GTX 1070 can give me more computing power?
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SerafimSalnikov

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Re: Why 2 Video Cards

PostTue May 30, 2017 6:36 pm

I received an answer to the same question I, asked BM support for.
There it is:

Thank you for contacting Blackmagic support.

We would recommend the use of the single larger GPU.
With Resolve 14, its best you go with a single GPU which is used for both UI and compute.

Using a single larger GPU provides more VRAM for Resolve to use.
GPU RAM or "VRAM" is not cumulative, meaning that if you have a 6GB GPU and an 8GB GPU, you do not have 14GB of VRAM.

If both cards were used for compute then Resolve would be limited to processing at the speed of the slowest GPU.
The larger GPU would also be limited to using the same amount of VRAM as the smallest GPU.
Therefore even though one GPU may have 8GB, if the other has 6GB, then both GPUs can only use 6GB of VRAM.

The only exception being if you have multi GPU system (for example 4), it might be better to have a GUI card for display and 4 dedicated cards for compute.

I hope this helps.
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Re: Why 2 Video Cards

PostTue May 30, 2017 7:39 pm

Peter Chamberlain wrote:There continues to be miss information about the use of GPU ram in Resolve.....If you have two fast, similar fast, GPUs, with v14 use both for compute even if one is also used for GUI....


Thanks so much for clarifying. I recently built a new PC with a pair of matching GTX 1080ti SC2 cards.. for a moment there I was worried that I had wasted monies.
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Gautam Chasmawala

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Re: Why 2 Video Cards

PostSun Jun 18, 2017 12:29 pm

Jake Melon wrote:Good question, I was just about to add a 4gb card just for GUI in addition to my WX 7100 but there is no need.

thanks!
jake


I was thinking about building my own system for Resolve, and was wondering what performance is like with the WX 7100. Could you compare it to anything else. Is realtime playback quick?
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Tony Martin

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Re: Why 2 Video Cards

PostTue Feb 13, 2018 11:38 am

Rohit Gupta wrote: Remember to go and configure the GPUs manually in Preferences as by default Resolve will exclude the GUI card for compute.

You were discussing multiple cards but in the latest iteration of v14 with only one GPU card installed, the GUI for compute box is UNticked - but presumably not excluded!

Surely if only one card is detected, it should be ticked and greyed-out. With only one card it has to use the GUI card for compute, does it not?
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Piotr Wozniacki

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Re: Why 2 Video Cards

PostTue Feb 13, 2018 2:27 pm

Rohit Gupta wrote:With Resolve 14, its best you go with a single GPU which is used for both UI and compute. It will give you better performance than a GUI + Compute card generally.

Only exception being if you have multi GPU system (for example 4), it might be better to have a GUI card for display and 4 dedicated cards for compute.


Rohit - are you saying that I'd get better performance replacing my 2x 1080 GPUs (one driving UI) with - say - a single 1080ti card? This would be great, considering how crowded my MoBo is now...

Piotr

PS. If thw above is true, clearing the 'use UI GPU for compute' - simulating lack of one of my 2 GPUs close enough - should give me better caching/rendering times than with my current setting, where the UI GPU is also used for computing, right? Obviously, this is not the case - so I (we???) must have misunderstood Rohit's revelation... Of course - using a single but most powerful GPU will probably perform better than 2 (or even 4 Rohit mentions), much weaker GPUs - but that's about it....
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Piotr Wozniacki

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Re: Why 2 Video Cards

PostWed Feb 14, 2018 8:21 am

Dear Rohit (or anyone with knowledge and experience):

The information in this thread about DR14 being optimized for a single, powerful GPU (doing both the computing and UI handling) rather than - say - two weaker ones has got me interested as it's still too early for completely new system here, and the current one has some compromises due to the X99 motherboard using all 40 lanes and not enough space inside the case, which made me relegate some components out of it using the 3M PCIe extenders. I'd be happy if I could get rid of one of my 2 1080 GPUs - but the question is:

- which more powerful GPU model would perform better than the current 2x GTX 1080?

Would the GTX 1080ti be enough? If not - which one: Titan X/XP, P5000?

And another question: for the best CPU/GPU performance balancing viewpoint, would installing a really fast GPU make sense while staying with my 8-core i7?

TIA

Piotr
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