FleurDuMal said:But, if you use FCP, Photoshop (come CS3) and, to a lesser extent maybe, Aperture, then you will utilise it. Video encoding also benefits from every extra core and Mhz you can throw at it.
Well, its not so clear cut. FCP itself won't work any faster (eg RT Render) than on a Conroe system (as demonstrated by benchmarks that show a dual woodcrest having no difference from a single woodcrest setup).
As far as encoding goes, its entirely dependent on the encoding algorithms. MPEG2 should be able to take advantage of all cores. H264 is notable for being piss poor at taking advantage of even just two cores, and that's on a one pass encode, a second pass is always done using one core only.
Photoshop's code base is notorious for poor scalability. It can use two cores relatively well, rarely going over 70-80%. When on a quad core, it takes 30% advantage from those extra two cores. I've read that on a 8 core system, the improvement would be near 8% for the extra four cores.
Unless Adobe rewire the PC and Mac versions from the ground up (highly doubtful), Photoshop will continue to scale abysmally.
As far as Aperture, I don't really know how well it does, for example, on a DP2.5 G5 vs a Quad2.5 G5. Would be interesting to see if there are heavy optimizations in the code.
Going beyond a single core is highly dependent on the way the coding is done for each software, and some things are just inherently serial. Most pro apps scale adequately to two cores, beyond that remains to be seen.
At the moment the real advantage beyond two cores is in multitasking. I personally think the sweet spot for performance, multitasking and longevity is a quad core system. I think as it stands with Apple's line up, a Mac Pro should last a lot longer than any G4 or G5 before it. Personally I'd prefer a Kentsfield xMac