FiringSquad, the gaming site started by Dennis Thresh Fong of Quake fame, has put together a daunting article examining the Xbox's hardware, comparing it not only to the PC architecture it owes its origins to, but also to that of the consoles it will compete against, the Sony PlayStation 2 and the Nintendo GameCube.There are far too many detailed points to mention them all here. However, one key item from the article is the idea that the shared-memory architecture, which was touted early on as its primary advantage against the PC, might not be such an advantage:

With a second vertex shader for extra geometry performance and an extra 33MHz, you might expect the XGPU to be hands-down faster than its PC sibling. What's missing from the equation is the fact that the XGPU does not have the same memory bandwidth in a GeForce3 PC setup. It's easy to see that the Xbox's DDR-RAM is clocked at 100MHz rather than the GF3's 230MHz. However, that's not the only disadvantage the XGPU faces. The Xbox has a shared memory architecture which means that memory bandwidth must be diverted for the system RAM.Looking at the published specs, the Xbox has a total of 6.4 GB/sec of bandwidth for the system and graphics. A GeForce3 with a Pentium III/PC133 SDRAM setup offers ~8.5 GB/sec, and the GF3 paired with an AMD Athlon on an nForce 420D with PC2100 DDR would give you 11.6GB/sec. Between the RDRAM and 2560-bit embedded DRAM, the PlayStation2 boasts a total of 51.2GB/sec!

Of course, as the saying goes, there are lies, damned lies, and hardware specifications. The proof will be in the playing. At least there's not too much longer to wait; about six weeks now.