My question is Radeon VII crossfire,
currently crossfire does not work in Dx11 it will be supported in later period.
My guess is that Vega 20 doesn't differ much from Vega 10(Vega64), so the profiles might work.
AMD Crossfire will work with DX9/10/11 applications using two or more AMD GPUs, but it is not Supported on Radeon VII
You can have the similar crossfire function with the MGPU, but it will work with only DX12/Vulkan applications using two or more GPUs (can be AMD or Nvidia if the developer has firstly enabled MGPU support) this is Supported on Radeon VII but reliant on the game developer to implement.
To be perfectly clear what you said here is the most important part " (can be AMD or Nvidia if the developer has firstly enabled MGPU support) ". MGPU in DX12 it is a DX12 software feature. AMD nor NVIDIA control whether it is supported or not, it is completely on the game developer to adopt. As it looks now not many are choosing to do so. I have seen statistics in the past of not even 5-10% of gamers even use more than one GPU so most find it not worth supporting anymore. Crossfire and SLI have been very poorly supported in the past couple years for the same reason under DX11.
Yeah I wonder why it's not allready done, Vega 2 shouldn't be much diffrent in approach(?), they would make a lot users happy.
But where did you get the info that is added later on???
I don't disagree that it should be possible. The bottom line is that both team red and green are moving away from this. Nvidia has long since moved away only offering it on it's flagship cards and team red has not had good support for crossfire IMHO since the Wattman drivers came out.
Bottom line is that with DX 12 not supporting it and only supporting Multi-GPU I think that the the card makers are glad to not have to support it. It was very few people that actually ever used it. Also realistically at this point most current sold cards are faster than the cards that did to sli or crossfire a few years back as a single card.
It was never a solution that had broad appeal. Even when it worked great on a few games having it enabled would cause issues with other games. I tried it and found it to be a pain. It would work great in one game, another game would have weird stuttering and other games not play at all. All issues you didn't have with single card solutions. For some though it was and great option and met their needs and others will I am sure say they never had a problem.
When it comes to DX 12 multi-gpu I just don't see many developers seeing the demand be high enough to ever support it.
When you think about it, from the get go AMD only planned to make Vega II in limited numbers to begin with, as at that price point only a relative few would buy, think how many fewer than that would buy 2. Yes some would but likely not enough to make it worth having to code the drivers to do crossfire for a version of DX that is now being replaced albeit slowly.
I know the motivations and the fact that multi GPU is handed over to the devs with dx12, but given the similarity of Vega 2 (GNC arch.), shouldn't it be an relative easy step to port it one time over again and stop it for RDNA? Most of the dx 9 and 11 work is done in existing games.
I have a long time experience with CF and I have to say with over 300 games installed, it covered 70-80% quite good.
I wouldn't be so keen on it if the perf. of a single GPU was enough for all games in 4 or 5K, but it isn't. You still need at least double the perf. of Vega 2 to play the most demanding games with enough frames. Two Vega's 2 in CF should be perfect with the high scaling CF often had.
But I understand it will eventually stop.
I don't disagree with you a bit that it should be possible. I am not a programmer so how easy it is I don't know. With the introduction of wattman the drivers and how the gpu's change speed and power is much more dynamic than they were on prior drivers. The new drivers have been adding lots of new features and my guess is that likely many of these things make it harder to balance across multiple cards. I doubt it is impossible, but again I think they just don't want to as again not many will even use it. I can't say that using multiple gpu's wont come full circle again but when it does I'm betting it won't be done like it was before. It had it's hay day, never worked great, at least not in a universal way and percentage wise very few ever used it.
Today I get a second Vega cheap, so I will be testing GOW4, Rise of The Tombraider, Shadow of the Tombraider, Hitman, Sniper Elite 4, Strange Brigade and Battlefield 1 which all should have dx12 expliciet multi adapter support. To bad Deus Ex Mankind dropped support it seems. Hopefully more will come in the near future, imagine Metro Exodus with it, this game should really need it to play at 5K
Rise of The Tombraider, Hitman, Sniper Elite 4, Strange Brigade and Battlefield 1 showed great scaling, GOW4 and Rise of The Tombraider refuse to start with
dx12 expliciet multi adapter, GOW freeze at start up and SOTT CTD with an error device hang". Esp. Strange Brigade is an example of how to implement dx12 expliciet multi adapter. Vulkan is such a great API for utilising GNC hardware.
Gears 4 and Gears 5 are poorly developed. Both are bug ridden.
I play the free Alien Swarm: Reactive Drop and its far less problematic, it's a community favority and there are so many maps it never get boring
I have an RX 480 and got room for more, but who knows what i will stuff into the box next