Xbox System-on-a-Chip
Jon Stokes (via John Siracusa):
It would have been easier and more natural to just connect the CPU and GPU with a high-bandwidth, low-latency internal connection, but that would have made the new SoC faster in some respects than the older systems, and that’s not allowed. So they had to introduce this separate module onto the chip that could actually add latency between the CPU and GPU blocks, and generally behave like an off-die FSB.