I hope by "Perform an atomic store of the new isa value." he means "Perform an atomic compare-and-set of the new isa value."

A64 doesn't eliminate conditional execution completely. It just pares it down to the basics: branch (obviously), add/sub, select, compare (for flattening conditionals like `a && b && c`).

Another thing removed from A32 was the optional shift on operand 2-- which was taking up 7/32 bits for most instructions.

This has a few more that were missed: http://nominolo.blogspot.com/2012/07/arms-new-64-bit-instruc...