Anandtech's been talking with some developers off the record re. X360 and PS3.
http://www.anandtech.com/video/showdoc.aspx?i=2461
I think he's being a bit sensationalist, and a bit too keen to compare unfavourably to PC architectures. I think it's a given that neither of these systems can have their performance exploited as easily as on a PC. It just seems, on his part at least (not the dev's), to be a big moan re. how they're not PC chips.
I also think the "waste of die space" comment re. Cell SPEs is extraordinary given that he goes on to discuss how they can "accelerate" physics. Even if that's all they could do, it'd be a big win IMO. Saying it only helps with handful of tasks isn't saying much without considering the sizes of those tasks (Physics is a big one). In his very own previous article, he mentioned Tim Sweeney saying that many of the things SPEs aren't useful for only take a small proportion of CPU time anyway..
Worth reading all the way through though. Also comments about the GPUs in there, but that still seems to be speculative territory.
http://www.anandtech.com/video/showdoc.aspx?i=2461
Right now, from what weve heard, the real-world performance of the Xenon CPU is about twice that of the 733MHz processor in the first Xbox. Considering that this CPU is supposed to power the Xbox 360 for the next 4 - 5 years, its nothing short of disappointing. To put it in perspective, floating point multiplies are apparently 1/3 as fast on Xenon as on a Pentium 4.
The Cell processor doesnt get off the hook just because it only uses a single one of these horribly slow cores; the SPE array ends up being fairly useless in the majority of situations, making it little more than a waste of die space.
We mentioned before that collision detection is able to be accelerated on the SPEs of Cell, despite being fairly branch heavy. The lack of a branch predictor in the SPEs apparently isnt that big of a deal, since most collision detection branches are basically random and cant be predicted even with the best branch predictor. So not having a branch predictor doesnt hurt, what does hurt however is the very small amount of local memory available to each SPE. In order to access main memory, the SPE places a DMA request on the bus (or the PPE can initiate the DMA request) and waits for it to be fulfilled. From those that have had experience with the PS3 development kits, this access takes far too long to be used in many real world scenarios. It is the small amount of local memory that each SPE has access to that limits the SPEs from being able to work on more than a handful of tasks. While physics acceleration is an important one, there are many more tasks that cant be accelerated by the SPEs because of the memory limitation.
I think he's being a bit sensationalist, and a bit too keen to compare unfavourably to PC architectures. I think it's a given that neither of these systems can have their performance exploited as easily as on a PC. It just seems, on his part at least (not the dev's), to be a big moan re. how they're not PC chips.
I also think the "waste of die space" comment re. Cell SPEs is extraordinary given that he goes on to discuss how they can "accelerate" physics. Even if that's all they could do, it'd be a big win IMO. Saying it only helps with handful of tasks isn't saying much without considering the sizes of those tasks (Physics is a big one). In his very own previous article, he mentioned Tim Sweeney saying that many of the things SPEs aren't useful for only take a small proportion of CPU time anyway..
Worth reading all the way through though. Also comments about the GPUs in there, but that still seems to be speculative territory.