Radeon Dual Graphics Performance with Kaveri and R7 250

Radeon Dual Graphics Mode, a technology based on Crossfire, has been supported by AMD’s integrated graphics products for quite some time (at one point before APUs existed, it was called Hybrid CrossfireX). It wasn’t until Kaveri, though, that integrated graphics performance became capable of playing games with settings you’d want to use, with reasonably acceptable performance. Any boost from there should be a good one.

With the Catalyst 14.1 beta, Kaveri now supports Dual Graphics Mode. However, the combination of APU and GPU is actually quite strict:

The top-end model of Kaveri, A10 7850, works with “Oland” based R7 series cards, which at this time means the R7 240 and R7 250. We’ll be focusing on the R7 250.

The R7 250 is equipped with 384 Radeon Shader Units, and has a 128 bit memory bus that can be outfitted with DDR3 or GDDR5. Interestingly, AMD suggests that the DDR3 version is the best one to use in Dual Graphics Mode with Kaveri. For this recommendation to work, the DDR3 version has to overcome the inherent performance advantage the GDDR5 version would have in Dual Graphics Mode. We may look at this at a later time, but for now we’ll be focusing on DDR3 performance.

Our weapon of choice for this review is the MSI R7 250 DDR3 OC model. This bumps up the boost clock speed to 1100 MHz from 1050, and the 2GB of DDR3 memory is clocked at 1800 MHz. This GPU, and those similar, sells for around $90. The GDDR5 versions are about the same, but come with 1GB of memory instead of 2GB.

Review Methodology

The purpose of this review is to take several games from several different genres, and see if Dual Graphics Mode creates a more playable framerate over stock performance with Kaveri’s integrated GPU.

Since Dual Graphics Mode only works with DirectX 10 and 11 games, there may be some cases where it offers no performance benefit at all.  We ran our entire suite of 10 games, but there is no reason to keep the “pure DX9″ games around, so they will be left out. Here’s a list of our game testing suite, and some information about them:

We will be leaving out Borderlands 2 and Witcher 2 for sure. Batman Arkham City is slightly different in that it has some DX11 features added to a DX9 engine. According to AMD’s documentation introducing Dual Graphics to us, Skyrim should receive a performance increase despite being a DirectX 9 game (they claim 61% in 1080p Medium). However when we enabled it, the whole screen just stuttered like crazy, and it was totally unplayable.

Note that in the case of Battlefield 4, the DirectX 11.1 engine was used instead of Mantle. Unfortunately the frame spiking issues we saw when we tested Mantle performance with Kaveri was made even worse when Dual Graphics Mode was enabled. This is all still very beta, so we need to wait for these issues to be resolved.

We weren’t one of the 5 or so sites that received the expensive and bulky FCAT testing equipment from Nvidia which allows one to see if there are any major frame pacing issues with AMD’s implementation of Dual Graphics Mode. We are still using FRAPS which, while not perfect, is still the best tool out there besides FCAT. We have to trust that AMD’s “Frame Pacing” setting in the drivers is functioning correctly; fortunately we have been able to confirm that at least one FCAT-equipped site has tested this function, and they found it to work just fine. Like Dual Graphics Mode, Frame Pacing only works in DX10 and DX11 games.

System Specs

How We Test Video Game Performance

Our gaming performance tests are probably a bit different from what you’re used to seeing on most sites. We test performance using real-world gameplay exclusively, and the results we look at are frame time measurements in addition to standard frames per second.

We have found that FPS simply doesn’t carry enough data to tell us truly how a given set of hardware actually feels when you play a game. A simple way to explain this is that any given 60 second segment of play-through may have 2000-3000 individual frames shown to the user. What FPS does is take all 3000 of these data points, and combine them into one overall number. Although the use of “frame rate over time” is better than this, it still takes those 3000 data points and turns them into 60. Because the variation of speed that occurs frame-by-frame and not second-by-second is what can make a game feel ‘stuttery’, even though the “FPS” is high any given second or minute, it is important to look at game performance in terms of these individual timings. For further explanation, check out Scott Wasson’s Inside The Second article on the subject. He is the one who spearheaded the whole movement into this type of testing.

Each game is tested using a 60 second play-through of a level with the intention of being repeatable and consistent. This is easier in some games than others, so our benchmarks are repeated 3-5 times to find the most consistent result. Once that result is found, we use that as a representation of performance. FPS is recorded, as well as individual frame times.

So What Settings Do We Use?

To determine which settings would be used to discover Dual Graphics Mode performance, we sought to run all games at settings that could be just barely considered as “playable”. Of course the definition to this is highly subjective, but for me the threshold is right around the 30 FPS level. The second goal was to run all games at “barely playable” settings at 1080p. This was possible in all games but two – Assassin’s Creed IV, and Crysis 3; those games were run at 720p instead, with settings that ended up being “barely playable”.

After that, the same settings were tested with the R7 250 by itself on the same platform. Finally, we enabled Dual Graphics Mode, to see what kind of performance benefit could be achieved, if any. More importantly, we need to see if it can take settings that are “barely playable” and make them feel more playable.

Without further ado, let’s get it on with the benchmarking!