There are ways around the supply issue without going to a battery, you just have to understand what you are dealing with as far as noise.
Back in the mid '80s I built my own enduro computer prototype. It was fully programable like an ICO and had an LCD dot matrix display. It was based on an Intel 87C49 micocontroller and Dallas smart clock, and coded in Intel Assembler. It basically worked on the bench with simulated inputs. The KDX200 bike supply was too dirty so I went with a battery but the consumption was quite high with the ICs back then. I got laid off from that company and lost after hours use of the development system/emulator so I was never able to finnish it.
That stuff was big $$ back then.