Rumors and some game developer comments (on the record and off the record) have Xenon's performance on branch-intensive game control, AI, and physics code as ranging from mediocre to downright bad. Xenon will be a streaming media monster, but the parts of the game engine that have to do with making the game fun to play (and not just pretty to look at) are probably going to suffer. Even if the PPE's branch prediction is significantly better than I think it is, the relatively meager 1MB L2 cache that the game control, AI, and physics code will have to share with procedural synthesis and other graphics code will ensure that programmers have a hard time getting good performance out of non-graphics parts of the game.
At any rate, Playstation 3 fanboys shouldn't get all flush over the idea that the Xenon will struggle on non-graphics code. However bad off Xenon will be in that department, the PS3's Cell will probably be worse. The Cell has only one PPE to the Xenon's three, which means that developers will have to cram all their game control, AI, and physics code into at most two threads that are sharing a very narrow execution core with no instruction window. (Don't bother suggesting that the PS3 can use its SPEs for branch-intensive code, because the SPEs lack branch prediction entirely.) Furthermore, the PS3's L2 is only 512K, which is half the size of the Xenon's L2. So the PS3 doesn't get much help with branches in the cache department. In short, the PS3 may fare a bit worse than the Xenon on non-graphics code, but on the upside it will probably fare a bit better on graphics code because of the seven SPEs.
In sum, the Xenon will certainly make the Xbox 360 a 3D graphics powerhouse. Though history suggests that the Xbox 360's games will probably never attain the level of graphical realism promised by Microsoft's pre-launch hype and portrayed in the pre-rendered "game demos" that were shown off at E3, gamers can nonetheless expect a significant advance in levels of graphical realism and visual immersiveness.
http://arstechnica.com/articles/paedia/cpu/xbox360-2.ars/1
At any rate, Playstation 3 fanboys shouldn't get all flush over the idea that the Xenon will struggle on non-graphics code. However bad off Xenon will be in that department, the PS3's Cell will probably be worse. The Cell has only one PPE to the Xenon's three, which means that developers will have to cram all their game control, AI, and physics code into at most two threads that are sharing a very narrow execution core with no instruction window. (Don't bother suggesting that the PS3 can use its SPEs for branch-intensive code, because the SPEs lack branch prediction entirely.) Furthermore, the PS3's L2 is only 512K, which is half the size of the Xenon's L2. So the PS3 doesn't get much help with branches in the cache department. In short, the PS3 may fare a bit worse than the Xenon on non-graphics code, but on the upside it will probably fare a bit better on graphics code because of the seven SPEs.
In sum, the Xenon will certainly make the Xbox 360 a 3D graphics powerhouse. Though history suggests that the Xbox 360's games will probably never attain the level of graphical realism promised by Microsoft's pre-launch hype and portrayed in the pre-rendered "game demos" that were shown off at E3, gamers can nonetheless expect a significant advance in levels of graphical realism and visual immersiveness.
http://arstechnica.com/articles/paedia/cpu/xbox360-2.ars/1
