CISC decoders must first determine how long the instruction is before they can even get started, wasting valuable nanoseconds. The last big difference I'll talk about between RISC and CISC processors involves how they interact with memory. The main memory in most computers takes much longer for a processor to access than memory contained on the processor itself. As such, it's much quicker to add two numbers that are stored on the processor than two numbers that are stored in memory. Instead, as I mentioned earlier, they have separate instructions that read the contents of memory, act upon them internally, and write them back out.
Registers are where all the action is, so to speak.
This is where the processor loads things it needs to act upon. It's also where the processor puts the results of all of its computations. RISC processors are loaded with registers, especially when compared to CISC processors. Cache memory sits between a computer's main memory and the microprocessor. It is much like normal RAM, but much faster to access.