Does adding a second GPU increase VRAM?

[Shinigami786]

I'm running a GTX 1650 4gb and a lot of newer titles require more than 4gb and I also stream so I need a lot more than just the base requirements, I have a second GTX 1650 that I scraped from and older system and was wondering if I could use them both to increase my VRAM or possibly separate the load maybe? Like OBS runs on the first one and game runs on the second one? Or if I'm not streaming is it possible for the game to use both the GPU's VRAM? And just out of curiosity do newer GPUs have this VRAM fusion technology by any chance if not my old one? 

[will0hlep]

10 minutes ago, Shinigami786 said:

I'm running a GTX 1650 4gb and a lot of newer titles require more than 4gb and I also stream so I need a lot more than just the base requirements, I have a second GTX 1650 that I scraped from and older system and was wondering if I could use them both to increase my VRAM or possibly separate the load maybe? Like OBS runs on the first one and game runs on the second one? Or if I'm not streaming is it possible for the game to use both the GPU's VRAM? And just out of curiosity do newer GPUs have this VRAM fusion technology by any chance if not my old one? 

SLI would (i believe, I'm not certain) allow you to add up the Vram, but it is now a dead/unsupport technogoly and always caused more problems than it was worth. (you'd need an SLI bridge as well I think)

(the crossed out info was wrong, see @xFluing)

[xFluing]

Just now, will0hlep said:

SLI would (i believe, I'm not certain) allow you to add up the Vram, but it is now a dead/unsupport technogoly and always caused more problems than it was worth. (you'd need an SLI bridge as well I think)

SLI never added VRAM together. There WAS a time where if coded correctly DX12 could do that although it wasn't worth pursuing as SLI and Xfire suck anyway.

 

What I think he CAN do is split the workload between the GPUs i.e. tell OBS to run on one video card specifically, while games are defaulting to the other although I think that's gotta be hard to do.

[will0hlep]

6 minutes ago, xFluing said:

SLI never added VRAM together. There WAS a time where if coded correctly DX12 could do that although it wasn't worth pursuing as SLI and Xfire suck anyway.

 

What I think he CAN do is split the workload between the GPUs i.e. tell OBS to run on one video card specifically, while games are defaulting to the other although I think that's gotta be hard to do.

dug a little deeper and confirmed your response. My answer has now been updated.

[Eigenvektor]

No, multi-GPU never increased VRAM, each card still only has access to its own memory. Aside from the issue that modern games typically no longer supprt SLI/CF.

 

The primary purpose of VRAM is to provide extremely fast access to data. Accessing the memory of another card would be constrained by PCIe bandwidth and would also increase latency.

 

Even PCIe 5.0 x16 would still "only" provide you with 64 GB/s (modern GPUs use at most PCIe 4.0)

 

A low end card like an RX 6400 already has 128 GB/s memory bandwidth and when you look at an RTX 4090 we're talking 1 TB/s.

 

Sharing memory across the bus simply wouldn't make sense for a use case like gaming.

[Shinigami786]

2 hours ago, Eigenvektor said:

No, multi-GPU never increased VRAM, each card still only has access to its own memory. Aside from the issue that modern games typically no longer supprt SLI/CF.

 

The primary purpose of VRAM is to provide extremely fast access to data. Accessing the memory of another card would be constrained by PCIe bandwidth and would also increase latency.

 

Even PCIe 5.0 x16 would still "only" provide you with 64 GB/s (modern GPUs use at most PCIe 4.0)

 

A low end card like an RX 6400 already has 128 GB/s memory bandwidth and when you look at an RTX 4090 we're talking 1 TB/s.

 

Sharing memory across the bus simply wouldn't make sense for a use case like gaming.

ok so adding Vram is not possible
can I at least make applications choose different GPUs for the load
like tell obs to encode on GPU 1 whilst the game runs on GPU 0?

 

[Eigenvektor]

1 hour ago, Shinigami786 said:

ok so adding Vram is not possible
can I at least make applications choose different GPUs for the load
like tell obs to encode on GPU 1 whilst the game runs on GPU 0?

From what I could find, you should be able to tell OBS which GPU to use, if you switch Output Mode to Advanced.

https://obsproject.com/forum/resources/nvidia-nvenc-guide.740/

Search for "Advanced Settings", you can see a drop down that says "GPU: 0"

Spoiler

 

For gaming, it depends on the game. Some games may allow you to select the GPU to use, if you have more than one. Though I would expect most should simply default to the GPU the monitor(s) are attached to.

[igormp]

On 9/25/2023 at 1:08 PM, Shinigami786 said:

like tell obs to encode on GPU 1 whilst the game runs on GPU 0?

 

Yes, but keep in mind that the encoder is already a different chip from the actual GPU core, so you won't notice any difference in performance by doing so (and might actually decrease performance since you won't have zero copy anymore).