Thursday, September 21st 2017

AMD CrossFireX Scaling is Actually Pretty Terrible with Mixed RX Vega

Yes, this is the third post today about AMD introducing multi GPU support for RX Vega with their Crimson ReLive 17.9.2 beta drivers but it had to be made. First up, the caveats- we were only able to test the driver on a CrossFire setup involving one RX Vega 64 and one RX Vega 56 GPU so results with two of the same may differ. Secondly, these are beta drivers so there is a level of lenience here I am willing to afford to AMD. That said, the driver which came with its own announcement and internal results had to show something good and this means showing good scaling across multiple games.

The driver allows CrossFire to be enabled with a mix of the two Vega 10 SKUs, and we set about testing a few games from our GPU benchmark suite using the same testing methodology as always. Tests were done at 4K to minimize a CPU bottleneck of any kind, and the games tested include some of the most popular games today including some that AMD themselves used in the announcement. However, after a few hours of testing, we can simply not recommend using the driver for CrossFire- at least for a mixed setup as we did. More on this after the break.
Enabling CrossFire with GPUs that are based off the same die and family but with a different shader count has been something AMD has done for a few generations now, and we continue to appreciate this remaining an option. However, this is no excuse for the performance we are seeing here, be it a driver issue or otherwise. As can be seen from the chart above, a lot of games not only show poor scaling relative to a single RX Vega 64 but actually negative scaling. The negative scaling can potentially be a result of Vega 56 slowing down the Vega 64 card here, but then we are back to zero to minimal scaling again. Of the four games that do, three were in AMD's results chart that went around earlier today as well. This is really disappointing performance, and to make it worse we also faced visual artifacts and display corruption in a few games including Witcher 3 (pictured), Prey and Dishonored 2. We also tried having RX Vega 56 be the primary card to see if that changes anything, and the results were within error margins more often than not with a few results actually being higher (5-10%) than with RX Vega 64 as the primary card. There was also a blue screen that greeted us during the switch, so do not attempt to do so often.

There is another interesting train of thought departing this station of results. AMD has had CrossFire profiles for the previous Polaris (and older) architecture GPUs for most of the games tested here, and they showed consistent, if not great, scaling with those older cards. But based on the inconsistent scaling across game titles here, it appears that AMD may have to create new CrossFire profiles for all games with their RX Vega GPUs based off the Vega microarchitecture. This merits more analysis and testing, but we are definitely curious whether this is indeed the case and, if so, what is the reason behind it knowing that Vega is an evolution of GCN, and not a complete departure from it.

AMD, with Lisa Su temporarily taking over RTG leadership, has a big challenge ahead with the enthusiast graphics solutions market and we can only hope the situation is better with 2x RX Vega 64 (or 56), else this is another thing that is not going to help them.
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73 Comments on AMD CrossFireX Scaling is Actually Pretty Terrible with Mixed RX Vega

#1
bug
Interesting. Of the games suffering from negative scaling, CivVI, Deus Ex and Doom were pretty much poster children for AMD.
Posted on Reply
#2
CAPSLOCKSTUCK
Spaced Out Lunar Tick
I am looking forward to seeing a complimentary piece about two matched cards.
Posted on Reply
#3
VSG
Editor, Reviews & News
CAPSLOCKSTUCK said:
I am looking forward to seeing a complimentary piece about two matched cards.
The two cards tested were review samples, so until aftermarket cards come in for review it may not happen here.
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#4
RejZoR
Why on Earth would you mix Vega 64 and 56 ? Just because it works, it doesn't mean it'll work well. Dual card setups NEVER worked well with two different cards. Why is this a shock to people like 20 years after dual card setups existed?
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#5
VSG
Editor, Reviews & News
RejZoR said:
Why on Earth would you mix Vega 64 and 56 ? Just because it works, it doesn't mean it'll work well. Dual card setups NEVER worked well with two different cards. Why is this a shock to people like 20 years after dual card setups existed?
I dare say different AMD cards that allowed CFX have had consistent, decent scaling in the past. My R9 290 and R9 290X, for example, performed very well together and I know I am not the only one there. Similarly, a quick search reveals positive, consistent scaling even as recent as Polaris.

Of course this does not mean things will be the same with Vega, as it clearly shows here, but the point of the test was to also see if the old CFX profiles carry over to Vega or not.
Posted on Reply
#6
Jism
RejZoR said:
Why on Earth would you mix Vega 64 and 56 ? Just because it works, it doesn't mean it'll work well. Dual card setups NEVER worked well with two different cards. Why is this a shock to people like 20 years after dual card setups existed?
In crossfire with different cards or setup(s), basicly the slowest card will take the lead. The faster card will be downclocked towards the slowest card to keep them in pair without having latency troubles or other issues.

I think this is more of a driver thing rather then how good these cards can scale. When crossfire works, they scale almost 100%.
Posted on Reply
#7
Th3pwn3r
Jism said:
In crossfire with different cards or setup(s), basicly the slowest card will take the lead. The faster card will be downclocked towards the slowest card to keep them in pair without having latency troubles or other issues.
So you're saying Vega 56 downclocks itself to Vega 64 speeds?
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#8
Prima.Vera
RejZoR said:
Why on Earth would you mix Vega 64 and 56 ? Just because it works, it doesn't mean it'll work well. Dual card setups NEVER worked well with two different cards. Why is this a shock to people like 20 years after dual card setups existed?
What are you talking about!? I was succesfully using for years a 5870 with a 5850 with awesome performance increase (when it was working).
Posted on Reply
#9
Jism
Th3pwn3r said:
So you're saying Vega 56 downclocks itself to Vega 64 speeds?
No, the Vega 64 will actually downclock towards 56.
Posted on Reply
#10
RejZoR
Jism said:
In crossfire with different cards or setup(s), basicly the slowest card will take the lead. The faster card will be downclocked towards the slowest card to keep them in pair without having latency troubles or other issues.

I think this is more of a driver thing rather then how good these cards can scale. When crossfire works, they scale almost 100%.
You people do realize they don't have the same amount of shader units, right?
Posted on Reply
#11
Th3pwn3r
Jism said:
No, the Vega 64 will actually downclock towards 56.
It was a joke, some will get and like it
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#12
Eroticus
I have no idea why AMD isn't blocking features like that by default like nvidia , so people won't bitch about how AMD is bad on the Internet ....
Posted on Reply
#13
Jism
RejZoR said:
You people do realize they don't have the same amount of shader units, right?
Yeah well they are on par anyway when 56 is flashed with the Vega 64 bios. It's really close anyway.

The big culprit of vega is that it's original design was aimed at compute and not gaming. The 56 still makes a good competitor against the 1070.
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#14
EarthDog
Youd think with the delay they'd have this ironed out a bit more... :)
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#15
evernessince
Eroticus said:
I have no idea why AMD isn't blocking features like that by default like nvidia , so people won't bitch about how AMD is bad on the Internet ....
People will bitch about AMD regardless. Nvidia releases crap drivers that Bork your OS? That's ok. AMD releases drivers that put a shortcut on your desktop? All of a sudden they are the devil. Nvidia has had far more driver issues recently and most people still somehow think Nvidia has better drivers.

Where was the outcry when Nvidia started requiring keys for more than two video cards and then just suddenly stopped supporting it all together? Fucking double standards galore.
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#16
EarthDog
People will bitch about anything. They have BOTH had their share of issues. In my personal experience, I have had better luck with NVIDIA. Certainly, others have had better luck with AMD. What is amazing is how polarizing the issue is when reality dictates NONE OF US have a FUCKING CLUE which drivers are ACTUALLY better.
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#17
Fluffmeister
Hell, a single Vega GPU isn't very exciting when it comes to gaming, and as turns out throwing two at it is just a waste of mining resources. :P
Posted on Reply
#18
Th3pwn3r
EarthDog said:
People will bitch about anything. They have BOTH had their share of issues. In my personal experience, I have had better luck with NVIDIA. Certainly, others have had better luck with AMD. What is amazing is how polarizing the issue is when reality dictates NONE OF US have a FUCKING CLUE which drivers are ACTUALLY better.
The only cards I have had fail on me were Nvidia, still my favorite but my main rig and daughter's computer have AMD.
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#19
FordGT90Concept
"I go fast!1!11!1!"
Only 4 of 19 games tested could justify the additional cost...21%. Pathetic.
Posted on Reply
#20
xkm1948
Good thing they are showing Raja the door. Everyday the Vega is becoming uglier and uglier. Polish a turd 1000 times and it will still remain a turd.

For people saying hybrid Crossfire isn't a thing you are dead wrong. People even crossfired FuryX and Fury which are both different in clock speed as well as shader units and texture units.


You want proof? Here you go. By AMD RTG employee Matt himself from AMD's own community forum

https://community.amd.com/thread/186648


More proof:
http://www.overclock.net/t/1611844/r9-fury-x-r9-fury-crossfire/0_100


Something is seriously wrong with Vega's design. I am sure at the point it is no use to patch a sinking ship.


2015 right after FuryX launch RTG is spun off AMD, then lead by Raja. Now 2017 with Raja giving two consecutive flops Polaris and Vega he is shown the door. I hope Lisa Su can correct the path of RTG before it is too late.
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#21
Batou1986
Oh look multi GPU support is a crapshoot still .... :rolleyes:
Its not really another VEGA issue its the same issue its always been with multi gpu setups
software support.
Posted on Reply
#22
R-T-B
xkm1948 said:
I hope Lisa Su can correct the path of RTG before it is too late.
RIP ATI.
Posted on Reply
#23
FordGT90Concept
"I go fast!1!11!1!"
ATI died in 2006. AMD killed it. And nearly themselves in the process.
Posted on Reply
#24
Zubasa
VSG said:
I dare say different AMD cards that allowed CFX have had consistent, decent scaling in the past. My R9 290 and R9 290X, for example, performed very well together and I know I am not the only one there. Similarly, a quick search reveals positive, consistent scaling even as recent as Polaris.

Of course this does not mean things will be the same with Vega, as it clearly shows here, but the point of the test was to also see if the old CFX profiles carry over to Vega or not.
The thing is I simply cannot get Crossfire to work under DX12 for my 290X and 390.
In DX11 the cards works pretty well, but in most DX12 games the 390 pretty much sits idle.
In fact not even Time Spy works for my 290X + 390 set up.
Same is true with Sniper Elite 4, crossfire works in DX11, but doesn't work in DX12, which is like the dumbest thing ever since I either get DX12 with Async, or DX11 with crossfire.
Posted on Reply
#25
OSdevr
If CrossFireX was working correctly there would not be graphics corruption, and I'm not sure it's a driver problem.
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