How much VRAM is enough

Some testing using OpenGL software running the same program but with different texture resolutions to use different amounts of VRAM. Tested with 640x480 and 1920x1080 on GTX 765m with 2GB VRAM using GPUz to report VRAM usage.

First note that drivers have an influence.

W7 x64 nVidia driver 312.29

Textures (MB)	OS Memory		640x480			1920x1080
	DRAM	PAGE	FPS	Dedicated (MB)	Dynamic (MB)	FPS	Dedicated (MB)	Dynamic (MB)
15	84	152	1640	25	27	437	47	33
58	145	275	1550	85	27	440	107	33
933	1312	2640	1460	1285	23	440	1307	29
1458	3897	4019	1460	1955	23	7	1879	29
2099	5368	5768	1100	1838	1021	350	1860	1028

You can see there's not much change in FPS vs texture size at the same display resolution except when exceeding the amount of VRAM. Seems to be a bug at the transition too in this driver while close to the limit where the result is 7 FPS. Note that a large amount of DRAM is also allocated.



W7 x64 nVidia driver 335.23

Textures (MB)	OS Memory		640x480			1920x1080
	DRAM	PAGE	FPS	Dedicated (MB)	Dynamic (MB)	FPS	Dedicated (MB)	Dynamic (MB)
15	46	131	2250	25	28	460	47	34
58	46	248	2200	85	28	450	107	34
933	40	2601	2050	1285	28	470	1307	34
1458	44	3975	2030	1955	28	475	1977	34
2099	1059	5737	1250	1838	1016	310	1860	1023

Some changes to the memory management with this newer driver, DRAM usage is kept to a minimum until VRAM usuage is exceeded.



W8.1 x64 nVidia driver 335.23

Textures (MB)	OS Memory		640x480			1920x1080
	DRAM	PAGE	FPS	Dedicated (MB)	Dynamic (MB)	FPS	Dedicated (MB)	Dynamic (MB)
15	39	117	1980	0	52	530	0	78
58	41	238	1920	0	112	495	0	138
933	46	2611	1920	0	1316	495	0	1341
1458	42	3983	1750	0	1938	530	0	2008
2099	1046	5723	1100	0	2858	350	0	2883

W8 reports all memory used for video under dynamic.



Note that "page" is used. How much page you have will be a combination of DRAM size and the pagefile size. This means if you want to take advantage of all the usable DRAM with the newer driver and use all your VRAM you need to set the pagefile size to twice the size of VRAM.

GPUz with W7 requesting more than 2GB VRAM



GPUz with W8 requesting more than 2GB VRAM



Here's an example with 16GB of DRAM and requesting 2GB of VRAM with the pagefile disabled.

This shows over 13GB of DRAM free but because there is less than 9GB of page left then less than 9GB of that 13GB of DRAM can be used. IOW 4GB of DRAM is unusable.


How much VRAM is enough will depend on the software running. You can exceed VRAM with a performance hit, this also caused FPS to vary much more between min and max in the above test. If you want to use huge amounts of VRAM and want to use all your DRAM use the newer drivers and make sure that the pagefile size is set high enough.

 

Interesting results. So what did you use to stress the system?

 

Those are interesting results. But enough for what, exactly? It depends on many things, including the game's settings.

I think 2GB is "good enough," 3GB is sufficient, 4GB is ideal, and 8GB is overkill, at least for now.

 

Just wrote a quick and dirty OpenGL application to project a 3 axis rotating ball with multiple textures with varying resolution. The higher the texture resolution the bigger the textures are and the more VRAM is used for loading them but the displayed projection size remains the same. Individual texture sizes ranged from 0.75MB to over 100MB. Maybe I should also mention it was a 32-bit program and only using 40MB of DRAM itself.

Enough for what? well for the application. As for games I think they would mostly design them around the majority of systems, not sure if it is worth designing for those systems with huge amounts of VRAM given the small percentage of people using them.

I hope the above also explains the use of page. For instance a game run on a system with 4GB DRAM using near 2GB of VRAM with the pagefile disabled would crash. With 8GB of DRAM only 4GB would be addressable and some of that is going to be taken up by the OS itself. Of course if using only a small part of VRAM then more DRAM would be available for use.

 

I noticed this myself on my Vaio Pro 11. It has 4GB RAM, granted it's an IGP, but pagefile disabled or even set to 1GB and many games wouldn't play at all. Enabled to auto it sets about 2.5GB to pagefile and everything works fine.

 

So to enable maximum performance and stability I should have 8GB pagefile? Is that how this works?

 

Not so much about maximum performance but if you want full use of 4GB VRAM and all your DRAM then yes.

Up to the individual to decide what is best for them really. For instance if your never going to use more than 1GB of VRAM then a pagefile of 2GB would be sufficient or if you never use that much DRAM that you can live with loosing that 2GB (assuming only using up to 1GB VRAM) then you need not bother.