I understand one of the limitations of 32-bit processors is the inability to easily address more than 4GiB of RAM, which is a present day need even for mainstream computing on phones, tablets and laptops.

**What are some other mainstream computing advantages of a 64-bit register size architecture as opposed to a 48-bit register size architecture?**

Please cite relevant sources or provide detailed reasoning in your answers. Number of bits which are powers of two are better does not provide a technical justification.

Of course if price were not a consideration then the more bits the better, also we obviously cannot predict distant future needs.

A wider bus may be able to move data more quickly but the bus size doesn't always have to match the register size does it? Also a CPU with more transistors and more lines may be forced to run at slightly slower clock rate due to physical limitations perhaps?

With 48 bits you can address 256TiB of RAM: plenty of space to be useful for at least the next few decades. It seems that, generally, 32 bit numbers are already plenty large for most integer and decimal calculations for mainstream programming, making 64 bit seem wasteful. 64 bit applications end up consuming more RAM and the processor itself ends up with a lot of wasted transistors in the ALU, control unit and bus for bits that simply aren't needed. All that stuff takes up extra silicon space which could be used to simply make processors smaller and cheaper or could be put to better use in the form of caches or additional cores.