Current consoles have multi-core CPUs but not enough RAM to get the full benefit. It's also taken a long time for human beings, who generally only consciously do one thing at once, to figure out how to program massively parallel applications.
The byte-swapping thing might hint at some form of backwards compatibility with the 360, as the PowerPC architecture in the 360 stores bytes one way, while the x86/x64 architecture stores them the other way around. This is called Big-Endian or Little-Endian, referencing Jonathan Swift's Gulliver's Travels, where two countries were at war over which end of a boiled egg they cut.
"You're giving me Asari Commandos? You're the best father a girl could wish for!" - Liara T'Soni