Ah, ok. That would makes sense. That's interesting.
It sort of depends on who you ask, but importantly, this is a legendarily bad Mac. Also, at the very least, the 603 is worse than the 603e, and the Performa 6200 and its variants were the slowest PowerPC Macs ever released. So, depending on who you believe, it really could be down to the cpu. There are certainly other issues, but that's the most painful one.