The concluding chapter of the Mass Effect trilogy is remarkable in that it's the first to be released simultaneously on all major HD platforms, with BioWare releasing Xbox 360, PS3 and PC demos earlier this week. Feedback we received from readers suggested that the PS3 build fails to match its Xbox 360 sibling, exhibiting major frame-rate issues - something we decided to put to the test.

Methodology in testing this sort of thing is fairly straightforward. In the absence of actual benchmarking tools for console games, we produce two separate tests to measure performance. In the first, we simply capture the exact same footage from each version. Mass Effect games are packed with engine-driven cut-scenes which gives us plenty of material to choose from: we decided to opt for the opening cinematic as it appears to pose various challenges for both Xbox 360 and PS3 engines.

General performance characteristics for Mass Effect 3 appear to be par for the course in comparison to its predecessors. Both versions appear to be operating with a 30FPS cap, and v-sync is engaged. The game is double-buffered, meaning that it is drawing the next frame behind the scenes while the current one is being displayed, with the framebuffer flipped on the screen refresh. The good news is that there's no tearing (well, not on PS3 any way - the 360 is sometimes a bit late with its update, resulting in an unnoticeable tear at the very top of the screen), but the bad news is that if a frame runs over budget, the game stalls until the next refresh.

This manifests in the 360 analysis as a smooth 30FPS frame-rate suddenly dipping for prolonged periods to a more jerky 20FPS. Now, with the PlayStation 3 game what we're seeing is more scenes operating over budget, resulting in longer, more sustained drops to the lower frame-rate. More than that, we also seem to be seeing that the PS3 version sometimes misses the 20FPS refresh, making the stall even more pronounced, resulting in some drops down to 15FPS - not good at all.

So how does this translate into the gameplay? Let's run some more analysis across the run of play from both levels featured in the demo.

"So is this unpolished, early code? In the most cases, playable samplers are entirely representative of the final product, but BioWare does have some form in releasing unfinished demo code on PS3 in particular."

It's pretty much the same story: frame-rate dips on both platforms (fairly consistent with Mass Effect 2, on 360 at least), but it's clearly the PlayStation 3 demo that is operating at a lower level of performance. It's something of a shame because in most other respects, the demo suggests that there's not very much to tell these two versions apart otherwise: both utilise a stunning new lighting system, and appear to feature FXAA anti-aliasing, which really suits the artwork.

However, the issues on PS3 do extend beyond the frame-rate; there's just a general sense that the code is somewhat unfinished. On scene changes, sometimes characters or textures noticeably pop-in - something we don't see on Xbox 360. And there's the odd bug too - check out this shot comparison and look at the background. All appears to be well on the Microsoft platform, but something bizarre is happening on PS3 - a shader bug or texture compression issue, perhaps.

Character and texture pop-in on the PS3 version suggests we're looking at unfinished code, and there's a general sense that the demo didn't enjoy the same level of QA as its 360 equivalent, as this shot demonstrates. Hopefully the PS3 version will be improved for its full release.

So is this unpolished, early code? Can we expect changes in the final game? In the vast majority of cases, playable samplers are entirely representative of the final product, but BioWare does have form in releasing unfinished code for its demos, on PS3 in particular. The Mass Effect 2 PS3 demo ran with v-sync disabled, improving overall frame-rate at the expense of image consistency - this was adjusted in the final version of the game. Similarly, the PS3 version of the Dragon Age 2 demo also saw some changes in its transition to final code.

Perhaps lending further credence to this theory is that the content we're seeing here isn't new: the introduction mission has been used in plenty of press material, while the second mission will be familiar to those who witnessed the Kinect voice command demonstration at Microsoft's E3 press conference. So hopefully we will see improvements to the final game - and of course, we'll be running a full Face-Off as soon as we can.