The Xbox 360 has a triple core CPU (code named Xenon CPU or XeCPU for short) which is a custom PowerPC-based chip designed by IBM for Microsoft...each core is independant (though they can also work on the same data in parallel) of each other and run at 3.2Ghz each...
These three cores are dual threaded so that gives XeCPU 6 hardware threads, each of which can run different types of data (Audio, Data Compression, AI, Physics, Xbox Live thread) or can even run the same types of data in parallel.....note that this doesnt mean XeCPU has the power of 6 CPUs because dual threading will not give you double the speed of a single thread running on the Core...
Each Core also has(EDIT)
two (or one....who the fuck knows) VMX SIMD (Single Instruction Multiple Data) vector unit(s) which is/are really good at floating point math...useful for next gen games...
The Xbox 360, unlike the Xbox, does not have a sound chip (though it *does* have specialized hardware to decompress WMA audio in realtime) as that capability can be run on one of the CPUs hardware threads....this is similar to the PS3 which also uses its CPU (Called CELL) to create realtime sound and music, in addition to other general computing and/or graphic tasks....
As impressive as the triple core Central Processing Unit is on the Xbox 360 (and it *is* impressive) it pales in comparison to the _true_ core of the X360.....the Xenos/C1 Graphics Processor...
Xenos/C1 was custom designed for Microsoft by ATI and it would be difficult for me to outline its many innovations and features in this space, but I'll do my best
Xenos/C1 is so much more than a GPU....it is the northbridge of the X360 architecture....it is the one chip in the system that is connected to everything..Southbridge, IO, XeCPU, UMA Ram, eDRAM daughter die....all of it goes through Xenos/C1
The first thing you should remember about Xenos/C1 is it has one type of shader processor (called Arithmetic Logic Unit or ALU for short) which can process not only pixels but polygons too and they can even work on some of the same kinds of things the XeCPU can (Animation, AI, Physics) in certain cases...this is known as a Unified Shader Architecture and Xenos/C1 has 48 ALUs in its unified shader pipeline
Most modern GPUs (including ATIs own new X1800 series) have seperate polygon(aka vertex) shaders and pixel shaders.....but since Xenos/C1 has a unified shader pipeline, all 48 ALUs are very efficient and flexible at creating game geometry as well as the surface textures that cover them and the particles and such that make up a scene...it splits the workload in a way where it attempts to reduce the situations an ALU will be idle....if the ALU is done working on polygons it can put on its "pixel hat" and get to work......in theory (though none of this has been benchmarked yet) a UMA is much more efficient than a traditional GPU shader pipeline, which might only have 8 polygon/vertex shaders and 24 pixel shaders for example....what if a game needs more than what 8 vertex shaders can provide?....what about less? The solution to this problem is what ATIs Xenos/C1 Unified Shader Pipline is trying to address...another intresting thing is the Xenos/C1 can dynamically allocate its UMA ALUs for every frame in a game in any given second in that game.....as if the hardware can reconfigure/customize itself for the graphic needs of every part of the game for every second in realtime....again, since Xenos/C1 has not been independently benchmarked it is not known how fast it is compared to a traditional vertex/pixel shader GPU....most likely, a Xenos/C1 ALU is not as fast as traditional vertex/pixel shaders which is probably why there are 48 of them in X360.....an ATI X1800 has 8 vertex shader ALUs and 16 pixel shader ALUs, for example...that is 24 ALUs total.....Xenos/C1 has *double* that!!!!
In addition to the main Xenon/C1 chip, it has a secondary, smaller chip which resides on the same GPU die...this smaller chip is also known as a daughter chip to which the main Xenon/C1 is the parent chip.....
The daughter chip has a small amount of customized silicon and 10MB of embedded RAM called eDRAM...Xenon/C1 has a pretty fast pipe to this daughter chip (32GB/sec) but the bandwidth *within* the daughter chip is CRAZY fast...to the tune of 256GB/s!!!
What ATI did with this daughter chip (and this is pretty crafty) is basically removed specific parts from a normal GPU graphics pipline that are demanding of high bandwidth (Z buffer, Anti-aliasing, Stencil, Alpha blend and more) and combined that with dedicated (and very fast) frame buffer memory, independent of the regular main memory (which is also unified and has to share bandwidth between the CPU and the Xenos/C1 parent chip) and put all of *THAT* on this special daughter chip away from the Xenos/C1 parent chip...this way, the main GPU is releved from some high BW operations, giving it more breathing room for other tasks....pretty nifty if you ask me
This allows all X360 games to have full scene Anti-Aliasing at little to no performance or bandwidth cost and which also makes it feasable for games to combine *that* with other high performance effects....such as High Dynamic-range Rendering (HDR) and more...
All in all, X360 seems to be a very balanced and efficient gaming hardware......its the Gamecube of next-gen, IMO and I mean that in a good way
As to how powerful X360 is compared to PS3......well that is a difficult question to ask right now.......when multiplatform developers are asked this question the answers range from "they are comparable" to "PLAYSTATION 3 is more powerful"....
However, the jury is still out because:
The final X360 hardware just shipped in August
Early PS3 kits were much more representitive of final HW power and therefore, more powerful compared to non final X360 dev kits (Alpha, Beta, Zeta, Omega)
Even if, as some devs say, PS3 is more powerful than X360, the accessibilty of that power
seems to be more difficult than with X360
As was the case this gen, the next gen Sony/MS hardware will have pros and cons to each....PS3 will not be more powerfull in all catagories nor will the X360 have the edge everywhere....they will both have their strengths and weaknesses, most of which will only be revealed by non-multiplatform games...
Final PS3 development kits are months from shipping (December) and even then, it will take many months of game development to show the improvements over current kits (PCI-E bus, slower CELL, slower XRDRAM, slower and less advanced off the shelf G70 GPU)
Because of all this, there is no apples to apples comparison of the two....more like a Doritos to Hamsters comparison
All that said, the PLAYSTATION 3 is the more powerful hardware in my opinion
