I asked in the Witcher 3 thread this question but never got an answer, would like to really know more about this please, maybe AMD Matt could briefly break it down
In default CrossFire mode both cards run at 60 procent. Under normal circumstances this would mean that you get about 20 procent more FPS than a single card. However, the reality is that you will get negative scaling with the default CrossFire mode. Meaning that you will get less FPS than you would with one card. If you enable ARF-friendly mode in CCC, the negative scaling goes away. Meaning that if your cards both have a gpu load of 60 procent, you will now get more FPS than a single card. This is the reason for the fact that you see an FPS-increase of more than 100 procent. By the way, i found a way to make CrossFire work (well, kinda). Have a look at this thread if you are interested and haven't looked at it already: http://forums.guru3d.com/showthread.php?t=399217&page=3
Thanks for the explanation. I see you have the same card as me I will try your sleeping dogs profile solution. But there should also be a driver release from AMD this week but who knows with them. I'm still left wondering though, if they are able to get almost 100% utilization with both cards, how is it they can't figure out a way to get rid of the flickering AFR mode introduces, is it impossible or something ? I'm sure people would love to have near 200% efficiency with 2 cards
I have no idea. I don't know how hard it is to make drivers and crossfire profiles for a game. It may seem like simple flickering for use, but i could be that it is really hard to fix.
AFR (Alternating Frame Rate) splits the workload amongst the GPUs by assigning a given frame to each GPU in the CrossFire Chain. So GPU1 renders frame 1 and GPU2 renders frame 2. In theory, you can get double the number of frames because GPU1 can jump straight to frame 3 without working on frame 2. In practice, this is reduced due to CPU overhead and other timing mechanisms which prevent you from always having something to work on. 3D Games are always working on ways to improve frame rate at the same time as providing the best possible visual experience. To do this it can do some cheats. The easiest one is to re-use data that has already been calculated and sitting in memory from the previous frame. So Frame 1 gets rendered fully, but Frame 2 could just render the differences and copy/paste the unchanged data from frame 1. This causes a headache for MGPU configurations because the data from Frame 1 is not on the same GPU that is rendering Frame 2. If you don't do the copy (and the game has no idea that it has to do so), you end up with flickering issues because Frame 2 is lacking the information in Frame 1. Since it is the GPU driver which is running CF, it needs to detect that a resource is missing and do a copy from the memory of GPU1 to GPU2. This takes time because the path and latency across the PCI-E Bus or CF Interconnects are much greater than between a given GPU and its own onboard memory. The more resources that need to be copied, the longer it takes for Frame 2 to finish and get presented after Frame 1. Certain CF profiles will skip the transfers that are unnecessary and in that case Frame 2 finishes very quickly because it has less data to compute than Frame 1. In that case your frame rate jumps. Normal CrossFire Profiles will always have some type of extra transfer for various games, but the AFR Friendly one only has very basic settings so it will probably be faster.
thanks for explaining it Matt.... I was really wondering how you guys are not able to get rid of the flickering that AFR produces to make it a viable option for crossfire users because of the raw framerate performance it offers. Now all that said, I only tested in Witcher 3, so I really probably don't know it all since I really have never used AFR before and this could have been a freak case. All I know is in some cases my framerates increased up to 100% in some cases over default crossfire mode. This could all be to unfinished drivers/patches, etc.... but almost doubling my framerates just by switching from default crossfire to AFR mode really got me wondering. I guess this is sort of what DX12 on Windows 10 will feel like, this type of performance jump
Don't mean to resurrect a dead thread here, but I Googled "AFR Friendly". Then this thread came up on the top of my list, as if it had the most information about it... Then I have been experiencing flickering a lot, since I started using Crossfire. Although, I am not using AFR mode. I was hoping that it may help prevent it. Does anyone here have any advice I could use? I have had it go away from patches from some games after complaining about it to help services, then I just thought I would try to play Total War Attila. Wow, give me a seizure... To think, I use to think that seizure warning before EQ1 was a joke... :bang:
Which games do you get flicker in apart from Attila (which I don't have) ? I can assure you though that 90% of flicker issues are solved by configuring profile and also in game settings. Especially AA type... The last game I had to fight with considering flicker was opengl id5 wolfenstein old blood. But even that runs butter smooth now without flicker. Just name your problem games maybe I can tell some settings
Forced AFR is indeed way faster in The Witcher3, esp. when moving! To bad its also cause flickering and some rendering errors....
I finally got crossfire working on my r9 290x with a stable 60fps with 2k texture packs, 60+ mods, no flickering, no yellow flashes, no issues....so far. I used AFR compatible and deleted the itint line in skse.ini . ***129303;***129303;
