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Japan tried to build an operating system for the entire world, then the US government intervened
(www.xda-developers.com)
This is a most excellent place for technology news and articles.
Original Nintendo DS had two different ARM CPUs for DS games ~~and the same CPU the GBA had~~ for direct compatibility.
The second CPU is the GBA CPU, but at twice the clockspeed (which can then downclock for GBA games). You're double-counting it and making it sound like the system had three.
The 3DS is the real funny one, adding its own new CPU alongside both the DS and GBA CPUs. So that's actually three.
I was probably thinking of the z80 then but that didn't get included