|
| Like the Playstation 3's Cell processor, the Xbox 360's Xenon processor
represents a fundamentally different approach to performance than that which
characterized the previous generation of consoles-and the previous
generation of PCs for that matter.
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.
http://arstechnica.com/articles/pae...xbox360-2.ars/7
|
|