Hmm... you raised an interesting question so I'm gonna look into it.
What I found is rather interesting. First of all, cloning the CPU is illegal so in a way I was right.
Then here comes the interesting parts:
AMD had reverse engineered the Intel 8088, 286 and 386 and produced their CPU based on the designs by Intel but it's not a clone.
Intel however reverse engineered AMD's 64 bit CPUs and produced theirs but still not a clone.
Thus the battles of the giants rage on to this day with their CPUs.