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Can Sys RAM be used as extra VRAM for graphics card?

Can some Gigs of system memory be used as an extension of VRAM for graphics card? ( Not iGPUs)

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No.

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They already do. If you pick settings that need more than on card, it can swap out to system ram. Performance will tank though, so generally not beneficial. Even if you had full width PCIe 4.0 you're only looking at 32GB/s off the card. That's likely slower than system ram, and on card vram of at least a mid range gaming card is order of magnitude bigger than that.

Main system: i9-7980XE, Asus X299 TUF mark 2, Noctua D15, Corsair Vengeance Pro 3200 3x 16GB 2R, RTX 3070, NZXT E850, GameMax Abyss, Samsung 980 Pro 2TB, Acer Predator XB241YU 24" 1440p 144Hz G-Sync + HP LP2475w 24" 1200p 60Hz wide gamut
Gaming laptop: Lenovo Legion 5, 5800H, RTX 3070, Kingston DDR4 3200C22 2x16GB 2Rx8, Kingston Fury Renegade 1TB + Crucial P1 1TB SSD, 165 Hz IPS 1080p G-Sync Compatible

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1 minute ago, porina said:

They already do. If you pick settings that need more than on card, it can swap out to system ram. Performance will tank though, so generally not beneficial. Even if you had full width PCIe 4.0 you're only looking at 32GB/s off the card. That's likely slower than system ram, and on card vram of at least a mid range gaming card is order of magnitude bigger than that.

Can you link some definitive information that Vram is pushed to system ram?

I've never seen this happen.

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8 minutes ago, ShrimpBrime said:

Can you link some definitive information that Vram is pushed to system ram?

I've never seen this happen.

I can't reference anything to prove it either way. We know already that if you pick something that needs more vram than your GPU has, performance tanks with all else being equal. The exact mechanism for that I don't know, but the practical impact is the same regardless.

 

In other words, I don't know if:

1, "vram" is allocated in excess of card capacity and driver/system managed swap out seamlessly to software

2, physical ram is not exceeded, software/driver level has more work to do to move things in and out manually

Main system: i9-7980XE, Asus X299 TUF mark 2, Noctua D15, Corsair Vengeance Pro 3200 3x 16GB 2R, RTX 3070, NZXT E850, GameMax Abyss, Samsung 980 Pro 2TB, Acer Predator XB241YU 24" 1440p 144Hz G-Sync + HP LP2475w 24" 1200p 60Hz wide gamut
Gaming laptop: Lenovo Legion 5, 5800H, RTX 3070, Kingston DDR4 3200C22 2x16GB 2Rx8, Kingston Fury Renegade 1TB + Crucial P1 1TB SSD, 165 Hz IPS 1080p G-Sync Compatible

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37 minutes ago, porina said:

I can't reference anything to prove it either way. We know already that if you pick something that needs more vram than your GPU has, performance tanks with all else being equal. The exact mechanism for that I don't know, but the practical impact is the same regardless.

 

In other words, I don't know if:

1, "vram" is allocated in excess of card capacity and driver/system managed swap out seamlessly to software

2, physical ram is not exceeded, software/driver level has more work to do to move things in and out manually

The reason I asked is because running 4K on my 2060, even maxing the gram, I have not noticed a large usage or any at all of system memory when the vram is full or over full.

 

Also have never seen this benching, but seldom do I run a 3D benchmark that would utilize all the memory on the video card, I prefer legacy.

 

As far as I am aware, video card software isnt designed to use system ram in any real way for rendering a picture. 

 

I suppose a lot of testing with some results would help, but this out of my league and or time availability.

 

Is there any way to really tell that the video driver is using system memory? If so, what would be a good way to measure this?

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1 minute ago, ShrimpBrime said:

As far as I am aware, video card software isnt designed to use system ram in any real way for rendering a picture. 

 

I suppose a lot of testing with some results would help, but this out of my league and or time availability.

 

Is there any way to really tell that the video driver is using system memory? If so, what would be a good way to measure this?

If we make an analogy with the CPU, from a software perspective it just asks for memory allocation. If there is insufficient physical ram, then swap file is used. I don't know if the same is done with the GPU. If there is insufficient VRAM, would the driver/system just start moving stuff in and out of system ram?

 

I suppose a controlled test could be performed if someone had access to otherwise identical video cards with different vram quantity. The RX580 springs to mind as a possible candidate in 4GB and 8GB models, where I don't think there were any other differences between them. Then suitable gaming settings would need to be selected to exceed 4GB and system ram usage monitored with the two cards. Someone must have done this at some point, but I'm not aware of a specific reference.

 

Above is a test I found comparing 5500XT 4GB vs 8GB. In short, some of the test cases showed no difference between them, others did. It seems logical that if the data fit within 4GB there would be no difference, and we would see a difference if the data exceeds that. Unfortunately there isn't detail beyond that, but with equal settings that extra data has to go somewhere. Where else can it go, if not to system ram?

 

I don't know about recent AMD cards, but certainly on nvidia cards the PCIe bus usage is monitored. You could indirectly compare traffic between known cases where the vram is or is not exceeded. As a further confirmation, the PCIe speed could be intentionally limited. I'm now thinking what software might be able to stress in such a way. GTAV I think had a VRAM requirement indicator, maybe Superposition benchmark? I haven't run that in a long time. Also think I saw it in Cyberpunk - don't own it, but was watching others try to get it working!

Main system: i9-7980XE, Asus X299 TUF mark 2, Noctua D15, Corsair Vengeance Pro 3200 3x 16GB 2R, RTX 3070, NZXT E850, GameMax Abyss, Samsung 980 Pro 2TB, Acer Predator XB241YU 24" 1440p 144Hz G-Sync + HP LP2475w 24" 1200p 60Hz wide gamut
Gaming laptop: Lenovo Legion 5, 5800H, RTX 3070, Kingston DDR4 3200C22 2x16GB 2Rx8, Kingston Fury Renegade 1TB + Crucial P1 1TB SSD, 165 Hz IPS 1080p G-Sync Compatible

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