[jecel]

Very good points. About ARM1, 2 and 3, if my memory from 4 decades ago is correct then the changes from 1 to 2 were a move to a slightly newer process node, replacement of "multiply step" with actual multiply instructions and the addition of the co-processor interface. 2 and 3 are the same processor, but with the latter adding a 4KB onboard unified cache, which allowed it to run at a much higher clock frequency.