The Xbox hardware was also quite advanced for its release date (2001). Many PCs at the time still had 100MHz FSB but the Xbox ran at 133MHz. The Xbox also had DDR RAM, not much of it (64MB), but DDR wouldn't be commonplace until the Pentium 4 and Athlon XP platforms a couple years later. Most PCs were still running regular single-channel SDRAM.
I've built a near-period correct PC with a later and faster CPU (Tualatin at 1.0GHz vs Xbox's Coppermine at 700MHz), more RAM (512MB), faster GPU (GF4 Ti4400), but it still can't achieve the raw memory and GPU bandwidth the Xbox had.
The fun thing about the RAM was that although the retail units only had 64MB, they shared the motherboard design with the devkits which had 128MB, and if you sourced a second set of RAM chips you could fully populate the board and build a 128MB retail unit. That was useful for some homebrew, and also made it possible to play games built for the Sega Chihiro arcade platform, which used the Xbox architecture but had the full 128MB of RAM installed and allowed games to use all of it.
If you were brave enough to replace a BGA chip you could upgrade the CPU as well, the stock one was an off-the-shelf 733mhz Pentium which happened to have a 1.4ghz counterpart, and surprisingly swapping the CPU out for the faster one mostly just worked. The faster chips were electrically compatible, but Intel only packaged those as socketed desktop parts, so people designed these wacky interposer boards to re-route the pins to the correct places on the Xboxes BGA footprint.
I love hackery like this that pushes hardware capabilities to their limits. It’s kinda like extreme overclocking, except somehow both more crazy and usually more likely to have an end result that’s practical for day to day usage.
I've built a near-period correct PC with a later and faster CPU (Tualatin at 1.0GHz vs Xbox's Coppermine at 700MHz), more RAM (512MB), faster GPU (GF4 Ti4400), but it still can't achieve the raw memory and GPU bandwidth the Xbox had.