ATI Sheds Light On Xbox 360 Backwards Compatibility

Technology website bit-tech.net has conducted an interview with ATI developer relations manager Richard Huddy, in which he reveals more details of how backwards compatibility is expected to work on the Xbox 360. Huddy has confirmed the inherent difficulty in enabling backwards compatibility in Microsoft's new console, given the change in manufacturer for both the Xbox 360’s CPU and graphics chip. According to Huddy, backwards compatibility was not deemed an important feature early in the Xbox 360’s design, with the assumption always being that it would be achieved through software. "They have implemented compatibility purely through emulation (at the CPU level)", says Huddy. "It looks like emulation profiles for each game are going to be stored on the hard drive and I imagine that a certain number will ship with the system. They already have the infrastructure to distribute more profiles via Live, and more and more can be made available online periodically." "Emulating the CPU isn’t really a difficult task. They have three 3GHz cores, so emulating one 733MHz chip is pretty easy. The real bottlenecks in the emulation are GPU calls – calls made specifically by games to the Nvidia hardware in a certain way. General GPU instructions are easy to convert – an instruction to draw a triangle in a certain way will be pretty generic. However, it’s the odd cases, the proprietary routines, that will cause hassle," he explains. Huddy also commented on the ongoing arguments concerning the relative abilities of the Xbox 360 and PlayStation 3. Naturally Huddy, as an employee of the company that makes the console’s graphics chip, is adamant that the Xbox 360 can more than hold its own, even going as far as to claim that it will be more powerful than the PlayStation 3. Rerfering to rival NVidia – who made the graphics chip for the Xbox and are now providing the same for the PlayStation 3 – Huddy suggests that Sony’s console may prove overly difficult to develop for, with a graphic bottleneck emerging as a result of the seven separate processor cores. "This time around, they don’t have the architecture and we do, so they have to knock it and say it isn’t worthwhile", he says in reference to NVidia comments against unified shader architectures. "But in the future, they’ll market themselves out of this corner, claiming that they’ve cracked how to do it best. But RSX isn’t unified, and this is why I think PS3 will almost certainly be slower and less powerful."