![[H]ardOCP](/images/blank.gif){kind=small}
- Date:
- Wednesday, March 05, 2008
- Author:
- Brent Justice
- Editor:
- Kyle Bennett
- Google +1
ATI Radeon HD 3870 X2 CrossFireX
The power of 4 GPUs is now possible with AMD’s ATI CrossFireX technology. We evaluate two Radeon HD 3870 X2 cards in CrossFireX on an Intel Core 2 Quad system, powering Crysis, COD 4, and UT3 seeing the gameplay experience produced compared to a Radeon HD 3870 X2 and a Radeon HD 3870.
Crysis
(DirectX 10)
We are using the full version of Crysis. Crysis is a first person shooter that is set in 2019. What makes Crysis unique is the amazing destructible environment and the on the fly customizability of your character and your weapons. Then there is always the graphics quality that will bring even the top end video cards to their knees. We will be playing Crysis in the default APIs for our system, which launches automatically in DX10 mode with the 64-bit executable. We have applied the latest Patch version 1.1 for Crysis which improves single video card and multi-GPU (SLI and CrossFire) performance.
As you progress through Crysis the game becomes more graphically demanding; first the scenic vistas, then the weather effects, and finally the final boss all lead your optimized playable settings of the first few levels to become unplayable. Our run-through in the graphs below involves 10 minutes of gameplay in “Assault_Crysis” the Harbor map. This map includes the transition from night to day, tons of explosions, particles, physics, AI interaction and water.
Note that in the graphs, we have lowered our redline to 25 FPS for Crysis. This game is demanding, and low framerates are impossible to avoid, gameplay is also different in this game to where 25 FPS and up feels very playable, very likely due to the efficient use of motion blur. Note that the down-spikes to 0 FPS in the graphs are due to the saved game points.
Crysis a very useful tool that shows when multiple-GPU performance is active by displaying “MGPU” in the devmode information provided. Devmode is achieved by placing the command line –DEVMODE in the shortcut for the game. As you can see in our game menu shot at the top MGPU mode is active with the Radeon HD 3870 X2 CrossFireX. Though Crysis supports multiple-GPUs, it does not currently scale as well as other games, especially past two GPUs. AMD told us to expect this, so they know that Crysis does not currently show off the power and potential of four GPUs currently. Still, we did see some gameplay performance benefits with four GPUs versus two.
Initial Crysis Experiences and GPU Activity
Our experiences came down to this, with two Radeon HD 3870 X2s in CrossFireX we found there to be greater GPU activity across all four GPUs by playing at higher resolutions in Crysis versus higher in-game settings. For example, we tried playing Crysis at 1280x1024 with everything on “Very High” and found the game to be unplayable.
Now, you would think that with the power of four GPUs we would easily be able to play at these settings in Crysis at such a low resolution. The problem is, the game is not taxing all four GPUs equally when gaming at lower resolutions, even though the in-game settings are maxed out. We can prove this by looking at the GPU activity graph that is now available in CCC. In the photograph below we have taken a picture of the GPU activity on one of the GPUs on the second video card while playing Crysis at 1280x1024.
As you can see the GPU activity for one of the GPUs on the second video card is 72%, not even a full 100% utilization of that GPU. This was the highest GPU activity we found on the second video card playing Crysis at lower resolutions. In fact, this activity generally was around 50% and lower while we were playing the game, showing that the GPUs just aren’t being pushed hard enough.
We found that in Crysis, increasing the resolution greatly improved CrossFire efficiency over increasing in-game settings. Therefore we were able to play Crysis at very high resolutions, up to 2560x1600, but we had to keep the in-game settings below “Very High” because “Very High” settings just weren’t playable, at any resolution.
With all of that in mind we found 1920x1200 to be the best balance of image quality and performance with two Radeon HD 3870 X2s in CrossFireX. At 1920x1200 we were able to have the all important Shaders Quality at “High!” With the Shaders Quality at High we had a phenomenal experience at 1920x1200. It didn’t stop there though; we were also able to turn Texture Quality to “High” which further improved image quality in the game on everything. The result was that we were sitting at a high widescreen resolution with a great gameplay experience.
With one Radeon HD 3870 X2 we found 1600x1200 with everything on “Medium”, except for Water, to be playable. That means that two Radeon HD 3870 X2s in CrossFireX allowed us to increase the resolution enable Shaders Quality and Texture Quality to “High” which was a large improvement over one Radeon HD 3870 X2. The measly Radeon HD 3870 single-GPU video card was playable at 1280x1024 with everything on “Medium.”
Other Playable Settings
1920x1200 wasn’t the only resolution the Radeon HD 3870 X2 in CrossFireX was playable in of course, just the one we felt gave us the best balance of performance and image quality. We of course test all our video cards at every resolution, to find the best settings, and so below is a table showing the playable in-game settings we found at 1280x1024, 1600x1200, 1920x1200 and 2560x1600 with two Radeon HD 3870 X2s in CrossFireX.
As you can see at 1280x1024 we found Crysis to be playable with everything on “High”, but not “Very High.” At 1600x1200 we had to set Game Effects, Post Processing and Particles to Medium. At 1920x1200 we of course had to turn several more things down to “Medium” but were able to keep Textures and Shaders Quality at “High.” We even tested all the way up to 2560x1600 and found that the game was playable if we turned everything to “Medium” except Game Effects and Particles to “Low.”
Now, the interesting thing about 2560x1600 we found was that performance was SLOWER when we set Textures to “Medium.” It might be a bug, but with Textures set to “High” performance was a LOT faster, and I mean a lot faster. Basically, at “Medium” Textures the game was unplayable, but at “High” Textures it was very playable. It either might be a bug, or it might be related to the Texture Streaming feature in Crysis when Textures are set to “High.”
Interesting Performance Phenomenon
We told you that Crysis currently does not scale well with more than two GPUs, heck, it doesn’t even scale that well with two GPUs compared to other games. We found an interesting performance phenomenon while playing the game. Basically, what we experienced was that when there was no action or AI on the screen performance was very high with two Radeon HD 3870 X2s in CrossFireX. However, as soon as we came across enemy AI and engaged them, performance dropped severely. We can display this below in a sequence of screenshots.
The screenshots below were taken at 1600x1200 with everything on “High” which we found to not be playable, and you will see why below.
The first three screenshots above were taken in the “Relic” mission, and show our character moving through the level in the "normal" progression that you would likely play. As you can see in the first screenshot we are at a very high 47 FPS, which would make you think these settings are playable. However, as we move down the trail and end up at the overlook where we are supposed to go down into we see our framerates drop to 26 FPS for some reason. Then, when we start engaging the enemy at the bottom here you see the framerate has dropped to an unplayable 18 FPS at these settings.
In the above screenshots we have another example of this in another level. We start off at a high 39 FPS but as we move into some action the framerate drops to unplayable levels.
These sequences of screenshots again prove why timedemos and graphics testing without the normal behavior of the game (such as having the AI frozen) wouldn’t represent a real-world experience of playing the game. As these screenshots prove, 1600x1200 with everything at “High” just isn’t playable unfortunately with two Radeon HD 3870 X2s in CrossFireX when the action starts happening. If you were to just stand in a forest with nothing going on though, you might think it is playable, when it actuality it is not. These extreme slowdowns were also experienced when running the game in 32-bit mode which we did try.