Earlier today, Firemint released a video showing a tech demo of its Real Racing game running on the iPhone 3GS, with 40 cars on the track rather than the existing game's six.

The developer has stressed that it's just a tech demo, with no plans for a commercial release. Is that true, though? You'd think Apple would be biting Firemint's hand off to get this onto the App Store to showcase its new iPhone.

We contacted Firemint boss Rob Murray to find out more, starting with the question of a possible release.

"It is possible to do a 3GS specific version, and we intend to explore it further at Firemint," he says, before pointing out that there's a commercial barrier beyond the pure cost of building, testing and maintaining two versions of the game.

"To get value from your 3GS-specific investment you would want to feature and promote its benefits. However, when you do that, at the same time you can very easily give the non-3GS market false expectations," he says.

"So if you do differentiate the 3GS, you need to think carefully about how much noise to make about it. If you make too much noise it may backfire with negative user reviews from non-3GS customers, if you don't promote it at all then you haven't really gotten full value out of your investment."

It's a conundrum. Perhaps in time, Apple will launch a dedicated section of the App Store for 3GS-optimised games - which might serve the double purpose of allowing developers and publishers to charge more for their games.

But back to that fragmentation issue. We were surprised that the performance gap between the 3GS and existing iPhones was so great, judging by Firemint's video. How big a problem is this for developers?

"All you really need to do is focus on the lowest common denominator and your app should only work smoother on the 3GS," says Murray.

"From what I have observed on the App Store, I don't think there are many apps that have pushed the limit of the existing hardware. For the vast majority of apps, there is little that they can do power-wise on the 3GS that they couldn't equally do on the prior models with just a little bit more care and optimisation."

However, he accepts that if developers use 3GS-only features like OpenGL ES 2.0 and the compass, that's a different kettle of fish.

"If you choose to use features like this then you have some thinking to do," he says. In the meantime, have a look at Firemint's 3GS-optimised Real Racing in the video below.