Yeah, I'm with you. Namely an explicit separation of load/store operation from operations that operate purely on the register file. Also, and I don't know how incidental this was, allowing for more registers that most instructions could encode as operands, with fewer implicit operands. Thus reducing the frequency of loads and stores. All of this reflecting the fact that the register file is much more readily accessible than even cached memory, something that I believe was not always true. At some point CPUs weren't running that much faster than the memory, so it was less of a big deal to be accessing it all the time.