Can system RAM be used as VRAM?

[DannyDem]

So couple of years ago, using system ram as VRAM was a bad idea as it would cause slowdowns and stuttering. But on the other hand with more recent ram, there aren't any major slowdowns even if you use system RAM at least from what I've seen. I noticed this with the recently released rise of the tomb raider, a guy was using a 980ti to play at 4k with all settings cranked up and the vram usage was pretty much reaching 100% which required the system to use system ram instead (this was observable as at 4k he was using 10gb ram while at 1080p only 6gb was being used) and suprisingly no slowdowns were visible (framerate at 4k was pretty much what a 980ti is capable of)

 

So what's your opinion on this? I do realise VRAM is normally much faster than the ram that we buy for our systems but watching these videos did create some major doubts tbh.

 

Here's the videos btw

 

https://www.youtube.com/watch?v=CQ6f0OyNivE

 

https://www.youtube.com/watch?v=ZMRoVoHUHfk

[don_svetlio]

Yes. A GPU can cache unimportant data in SYS RAM to free up VRAM if need be

[Godlygamer23]

Well, IGPs do use system RAM as VRAM right now. And if you look at the system information in NVIDIA's Control Panel, it'll show Shared System Memory.

[AlTech]

Snip

 

If they run out of physical video ram they tend to page to the HDD. IDK about regular ram though.

[Godlygamer23]

If they run out of physical video ram they tend to page to the HDD. IDK about regular ram though.

System RAM pages to the hard drive.

[AlTech]

System RAM pages to the hard drive.

 

I was saying VRAM pages to HDDs.  I meant IDK if  VRAM pages to Regular RAM before or after HDDs.

 

Sorry for not being specific. I know RAM pages to HDDs unless you disable it.

[Godlygamer23]

I was saying VRAM pages to HDDs.  I meant IDK if  VRAM pages to Regular RAM before or after HDDs.

 

Sorry for not being specific. I know RAM pages to HDDs unless you disable it.

From a technical perspective, I think it would make more sense to have VRAM page to the system RAM because of how bandwidth-hungry graphics cards are.

 

I mean compare 224GB/s to a measly 500MB/s for sequential performance on SSDs. Even slower RAM can achieve 10GB/s which is substantially faster. Just my thoughts.

[Nena Trinity]

Yes the iGPU normally does and yes the dGPU will if its out of VRAM, so double yes yes!

[bomerr]

DDR4 probably helps a lot because of the faster speed. Similarly it's quad channel too. 

[AlTech]

From a technical perspective, I think it would make more sense to have VRAM page to the system RAM because of how bandwidth-hungry graphics cards are.

 

I mean compare 224GB/s to a measly 500MB/s for sequential performance on SSDs. Even slower RAM can achieve 10GB/s which is substantially faster. Just my thoughts.

 

Well IDK. If so then in theory I would have some fast perf when I run out of VRAM. Since I have quad channel DDR3 that's 51.2GB/s . Not bad if true. Still wouldn't be that fast though.

[AlTech]

Yes the iGPU normally does and yes the dGPU will if its out of VRAM, so double yes yes!

 

So that's why I got loads of more FPS when I jumped to 16GB! I got like 30 fps more from 8Gb -> 16GB.

 

and my friends couldn't explain it. Granted they use 8Gb ram.

[Nena Trinity]

So that's why I got loads of more FPS when I jumped to 16GB! I got like 30 fps more from 8Gb -> 16GB.

 

and my friends couldn't explain it. Granted they use 8Gb ram.

Yes but system RAM will always be slower than VRAM!

[jjohnthedon1]

DDR4 probably helps a lot because of the faster speed. Similarly it's quad channel too.

Is ddr4 and ddr3 not the same at the same speed ie both at 2400mhz ??

[Godlygamer23]

Is ddr4 and ddr3 not the same at the same speed ie both at 2400mhz ??

DDR4 achieves more bandwidth but has higher latency.

[bomerr]

Is ddr4 and ddr3 not the same at the same speed ie both at 2400mhz ??

 

A lot of the DDR4 RAM is now 3 Ghz. Also very few people have 2400 Mhz. 

 

DDR4 achieves more bandwidth but has higher latency.

The thing is true latency = clock cycle time * cas latency.

 

http://www.crucial.com/usa/en/memory-performance-speed-latency

 

DDR3 1600 CL 9 = 11.25 true latency

DDR3 2400 CL 11 = 9.16 true latency

DDR4 3000 CL15 = 9.9 true latency

DDR3 3400 CL 16 = 9.44 true latency 

 

So DDR4 latency is only slightly worse than the top-end DDR3 ram but more importantly better than most mid-range DDR3 ram.