@NJ5
Anyone who uses most animation middleware packages, or physics middleware, etc. can and will use all 6 available SPEs (the 7ths is not usable by games). There's no reason not to. You just are going to have trouble using them all the time, because not all game tasks are covered by middleware, and not everything is embarrassingly parallel. Its not impossible to use them more, however -- as KZ2 demonstrates. Why they don't use 6 is beyond me... its possible that the graph is outdated, or that the other 2 SPEs are off doing something uninteresting in the background, but in real-time (like audio, or streaming work), and that they didn't care to show it on the graph.
Like any parallel system, anything that can be done in parallel (like animation processing, a very commonplace example) can be shotgunned on the SPEs, via middleware at the very least. Therein lies the Cell's advantage over the Xenon. Which is better, double-barrel shotgun (or up to 5 slow-RoF barrels, not 6, because one of the Xenon processor threads needs to manage the operation), or 6-barrel, high-speed minigun (the PPU thread managing them is different, and I suppose there is one more PPU thread to spare as well)?
Beer says that these operations are frickin' fast, esp. 3D vector math stuff (hence some previous posters' "GPU" comparisons), when done on all 6 SPEs in parallel. Beer is good for you, and never wrong.
