Nintendo DS did something similar, with the GBA’s ARM7 running in conjunction with the DS’s ARM9 and acting largely as an I/O coprocessor (IIRC) and handling ba

Nintendo DS did something similar, with the GBA’s ARM7 running in conjunction with the DS’s ARM9 and acting largely as an I/O coprocessor (IIRC) and handling backwards compatibility. The Wii and Wii U go a little further; in addition to the main PPC CPU, there’s an ARM core handling auxiliary tasks (mostly security and I/O related, but it’s also involved in early boot IIRC). That one’s not there for backwards compatibility; it’s purely there as a coprocessor.