Hi everyone,
I have questions about VRAM;
Is it possible to allocate more memory to my graphic card!? If yes, how much it would be effective in rendering process and its performance!?
Thanks 
What do you mean by “allocate more memory”? Do you mean allocate more system RAM as a spill over for VRAM?
In terms of performance. You need enough VRAM to contain the entire scene you are trying to render. If the scene exceeds your total VRAM capacity you will experience slow downs or worst case it will not render on GPU.
Yes, allocate more system RAM as a spill over for VRAM
I imagine that even if you could get your GPU to use system memory, the latency issues would make CPU rendering faster in the end.
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Then your render will slow. RAM to GRAM transfer is costly operation.
I do not think it is possible to change this by altering windows settings.
I believe the value changes based on the amount of system RAM you have, and from what i have seen it appears to be 50% of system RAM.
E.g. I have 64GB of RAM. My shared VRAM pool is 32GB, but my card is a 4GB card.
If you don’t mind me asking what has prompted you to ask about this? If you are having any problems there may be other ways of solving it.
on AMD VEGA, there was an option called HBCC Memory that permitted to allcoate system memory to it… Will admit though I do have VEGA i haven’t had the need to use it, so unsure if it actually works as I expect in Blender.
On next RX 5xxx and 6xxx that option is no longer available. 
unsure about nvidia.
Any new solution for this, why more RAM (DDR4 in my case) can’t use for additional storage? RTX 4070 12GB and almost every time: “GPU memory full” when trying to render. Last solution was to select resolution for screen to 480p then it started to render, because usage of VRAM dropped about 100Mb. But only couple of frames and then need to restart Blender and again couple of frames.
I also hope that in some Blender-version there would be possibility to select only that objects, materials, hairs that are seen in rendered frame and upload only this one to GPU memory (VRAM)…
If you are running out of VRAM, another solution you can try is enabling the simplify option in render settings which will reduce the maximum texture resolutions and thus reduce VRAM use. Most times you won’t even notice this reduction in the final render, unless you are rendering some very close up detailed shots of the object.
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What type of scenes eats 12Gb of Vram ? Is it optimized ?
I think every scene I made. Now scene where two sheeps with hairs. Working with at least FullHD, trying with 4K. Optimized all what can (also memsaver-addon), but no help, I think 12Gb is used in any case… Now added 3060 with this 4070 and can now render about 5 frames and then restart Blender and more 5 etc. Waiting black friday to get maybe 4080 with 16GB…
*edit: This is one of rendered frame:
Yes, this option is almost always enabled. Now with these:
First it was Max Subdivision 4 and Child particles 0.7, Texture limit 4K. It was possible to render two frames, after that dropping more…
Now I have 3060 for Windows and 4070 only for Blender. GPU memory usage is 514mb before rendering only faces of sheep and all other objects (even collection of trees, plants, other sheep etc.) are disabled after frame 253. I can render often 1-3 frame before “gpu memory full” is here waiting. Tried also rendering from command prompt, but memory is full there too. Memsaver doesn’t help att all, I can’t understand why Blender takes too much GPU memory every time, and every time more and more…
Now rendered frames 200-263, but no way to render frame 264 anymore.
frame 200
frame 263 (frame 264 is only continuing)
I hope that somebody will come up with idea how to workaround GPU memory limitation problem in Blender. 
Is the only reason again greed why Nvidia is not doing cards with interchangeable ddr6? 
4070 (used) price was 550€, but 4080 is asked here 1000€, even it price should be 870€, same with 3090 price should be 600€ but asked 750€ + more power consumption 50€/year. (Price based on points in Blender open data)…
Split the scene using the scenes options and render the foreground and backgrouns separately.
Speed is the reason. Interchangeable VRAM would be slow on a GPU.
You should investigate this thread. There is no such issue running Linux. Perhaps you could have a dual boot solution and avoid the 20% penalty.
Also, keep in mind that the card connected to the display, will have a bunch of its memory eaten by Blender itself. So, if you have a 3060 and a 4070, both with 12gb, the display card will have 3-4 gigs taken by the Blender instance, meaning only the second card will have access to it’s full memory pool. If you tried to render the scene using both GPUs, the display card will run out of memory and you will error out.
Solutions.
You could try using only the second card as a render device for heavy scenes. So have your 3060 as a display card, and the 4070 for the renders.
Another option, if you want to have two cards running at the same time is to run devices with different amounts of memory. Like the 4080, its 16 gigs will accommodate the Blender instance, and likely have the 12gigs left for rendering. That way it can participate in the render process together with the 12 gig cards.
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Ok, thank You. But I think it would be too complicated to do in every scene.
I ordered used 4090 from Ebay now, hope that helps.
Thanks.
I think that I tried wit POP! OS and had same problem “GPU memory full”!? I am pretty sure…
I had this GPU used exactly like You said, but even then only couple of frames rendered and after that need to do again.
And problem also was that Windows 11, I think, did not figured out how to use both gpu fans. Fans worked good in bios and when starting, but in Windows 3060 fans stopped if temperature was lesser than 60 celsius. One time at night found that Windows was rebooted itself during rendering and 3060 have about 90 celsius temperature been there (fans stopped still) I think one hour.
Easiest (and expensive) way was order used 4090, it would come in friday. Hope that will help, because this memory problem is ruining all work…
The 4090 should do the trick for sure, however I would still look at the scene itself. Perhaps there are more efficient ways to have the same visuals. Like, for the hairs, perhaps particles are not the answer, perhaps planes with alpha channels and textures is the way to go.
Most of the time, there are ways to work around the memory limitations. The importance of optimization cannot be overstated. Without much consideration it is easy to max out even a powerhouse like the 4090.
As for fan control, have you tried MSI afterburner? You can tweak various parameters of your card pretty easily. Just don’t forget to have it running in the background, otherwise it does not have an effect.
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Thanks again. Planes with alpha channel - have to check what is this. I think that with particles or with addon called BGEN GROOM doing hair is easy, but take much resources, like You said.
I had Afterburner installed, but affected only for 4070, not 3060 (it was grey there, pictures here). But I think (pray and hope) that 4090 will be enought that can sell these others…
If you can get avoid motion blur, that will help a lot.
Lots of hair curves + motion blur is a very memory intensive configuration.
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