2 Different Graphics Cards in One Computer

[Duxwing]

Hey Forum,

I found a graphics card on one of my shelves and want to install it alongside my current one to improve my game performance.  Although the graphics cards are slightly different, precluding a bridge, I have read that DirectX12 lets game developers work around this problem by building games that can use several different graphics cards at once.  Would installing the second card be worthwhile?

Technical Details:

-Current Card: GeForce GTX 780Ti 4GB

-Found Card: GeForce GTX 780 3GB

-Installation Cost: $40

 

[pxi]

You might want to have a look at this thread a quick web search threw up: https://forums.evga.com/GTX-780-and-Ti-for-SLI-m2153776.aspx

The tl;dr is that the two cards likely wouldn't work in a SLI configuration (which is what I presume you mean by a bridge) unless they're of the same DEV number.

As for DirextX12, I can't speak to that as I really don't know the ins and outs of it, but if it does allow you to use 2 different graphics cards outside of SLI, you'd still be limited to games that use DirectX12.

Also you include cost of installation.  You are aware that you'd be paying $40 to have someone unscrew a couple of screws, take the side off your computer, plug the card in, and re-assemble?  Not my place to tell you how to spend your money, but it's a process that's easily doable by the end-user imo.

[qzgy]

I'm more curious about if your power supply can handle it...

As for 40$ for instillation - It takes about 10 minutes. Its basically plug stuff in and secure with screws.

[Elthy]

DirectX12 only supports multiple different GPUs if the developers programmed the game with this in mind, which afaik didnt happen yet. Since MultiGPU is dying anyway noone will support it in the future.
Classic SLI wont work since those are different cards, but even if it did it isnt worth the hassle. The support is awfull, only few games support it, the scaling is bad and you get microstuttering.

If you need more graphics power you should buy a new GPU.

[YNM]

$40 installation ? Seriously ? Does it need extra cooling or is it located very close to other important fragile bits (processor, battery etc.) that's in a very hard to reach place and needs properietary tooling or what ?

 

Truer to what OP asks, I don't think it's possible. AFAIK GPUs have their own slot for the display to connect to it, otherwise it's not used, so you can't connect 1 display to 2 GPUs. Unless you have multi-screen setup or so (which I have no idea how the extended ones work !), I don't think it's feasible in any way.

Edited September 2, 2017 by YNM

[Duxwing]

Thanks for the replies!   You have persuaded me not to add the card unless I encounter bottlenecks years from now.  In response...

1) I would add the graphics card myself but would need to move bundles of cables that were zip-tied together and secured to the case by Geek Squad when they upgraded my rig years ago.  I might also need to move the hard drive and its cables, because the card would reach from the back of the tower to the front.  I am not confident in doing this. 

2) My power supply is 1,200 Watts.   If it would not have enough power, then I doubt I could find a bigger one, much less fit it into my computer.  It will have to do.

3) I too have noticed that Multi-GPU, whether enabled by the hardware of a bridge or the software of DirectX12 or Vulkan, is not supported by many games.  That said, they are new.  Would you mind showing me where you learned that multi-GPU is dying?

 

[Elthy]

11 minutes ago, Duxwing said:

3) I too have noticed that Multi-GPU, whether enabled by the hardware of a bridge or the software of DirectX12 or Vulkan, is not supported by many games.  That said, they are new.  Would you mind showing me where you learned that multi-GPU is dying?

Look at this link: https://www.3dcenter.org/news/sli-und-crossfire-eignung-aktueller-spieletitel-auf-schwachem-niveau

Its german, but the table at the bottom shows which games released this year had SLI/Crossfire support. There arent many, and even with support you can see that the performace gain isnt that great. Dont forget, those are pure FPS, if you substact the lower percieved frames due to microstuttering the benefit gets even smaller.

[Randox]

I was running two cards for a while, but I pulled the second card out for the summer for heat considerations, and because it was mostly making things complicated.

In my case I was running two AMD cards. My main card is an RX 480, and I was running it alongside an HD 7950 as an independant second card.

 

So, first problem is graphics drivers. Windows 10 (and I think Windows 8) don't allow you to install more than one set of graphics drivers. I discovered this when I tried to use an HD 6770 instead of the 7950. AMD drivers are sequential releases, each of which supports some range of cards. In the case of the 6770 and 480, there is no AMD graphics driver that supports both cards, so they cannot be used together in Windows 10. The 7950 though is one of the HD 7xxx cards that was rebranded for the R9 2xx series of cards, which makes it recent enough to still be supported in the most current drivers. Problem solved, though once support for the 7950 ends I would be forced to use an older driver to run the cards together.

Second problem is how windows works. Windows will allow you to designate either graphics card as the Primary Graphics Adapter The primary graphics adaptor will, by default, do 100% of the rendering for every screen connected to the computer regardless of which GPU the monitor is actually plugged into, and there is a serious penalty for cross rendering (when one GPU renders the screen and sends it to another for display). Some programs, mostly games, allow you to select which graphics card to use. For all other programs, you have to set the desired GPU as primary before launch the program. The same situation exists for audio devices if you wanted to play background music over speakers while listening to game audio through headphones.

 

As far as performance gains go...to my knowledge no DX 12 title exists that takes advantage of asyncronous GPU's. BUT, if like me you say, like to watch LP's on Twitch or Youtube while playing something like Euro Truck simulator then you can boost performance by having a different GPU take on each task. I could set my 7950 as primary, open Chrome, then set the 480 as primary and open up a game. Chrome is now using my weaker card, and whatever rendering it does will have no impact on my 480, which is now free to dedicate 100% of it's efforts towards my game of choice.

In real terms though, video rendering was about all that ever got offloaded, and both of the cards I am using are more than strong enough to render videos while gaming. It was just a complicated way to use more power and interfere with airflow into my gaming card. There is also a small performance hit to both cards, the 480 in particular, since my CPU only has 16 PCIe 3 lanes (so installing a second GPU cuts both down to 8 lanes. It's enough to potentially shave 3-4 fps off the 480).