How many bits should the processor memory registers have?
Whatever you want! But you must justify your choice (say why you did it). If you want a 42-bit word – that is ok (if you have a good reason). There are no restrictions on the architecture. Is there any restriction about the instructions we can implement in our instruction set? For example can our processor have for loops? This is a very good question. You can create ANY feature you wish (as long as you explain it and say why you are doing it). Such features would count as ‘clever ideas’ in the design of your ISA. For example, some may decide to do clever things with registers – make them indexable – or use windowing/shadowing/banking techniques to increase the apparent number of registers.
