Commodore infamously used TI chips in their calculators too, leading to the situation where Jack Tramiel was getting massively undercut by TI using the same chips in their own TI calculators for less. Buying the ailing MOS Technology gave him the vertical integration he wanted and enabled him to force TI out of the home computer market only a few years later. Revenge is such a dirty word.
Now we just need that one cool article about the Sinclair Scientific Calculator. It was a scientific calculator that was made to run on an underpowered chip intended for regular four-function calculators.
@kens beat me to it-I too was going to suggest Ken Shirriff's "Reversing Sinclair's amazing 1974 calculator hack". The page has a Sinclair Scientific emulator that displays the running, underlying calculator chip instructions.
I bought the Sinclair Scientific in 1974 for a physics lab class in college. It was much less expensive than the TI and HP scientific calculators of the time, but it was painful to use in the lab class. I subsequently changed majors, so I only had to bear with it that first year, but, all these years later, I'm still in awe of what Sinclair achieved with it though!
I came to post the same link earlier. My mind is kind of slow these days and it wasn't until a few hours later that I made the connection with your username. I am not worthy!!! --a long-time reader