On a related note (pun intended) I once had a problem with one of these synths and its rubber contact strip. I would hit certain keys then hear a neighbor note or the same note an octave away. I thought there was a short in the scanning circuitry (I had resoldered some joints that appeared weak earlier by a ribbon connector for the keybed.)
Turns out the rubber contact strip was installed inverted. I think this one didn't have notches to make sure it was oriented correctly. After flipping it, notes sounded as expected.
I really appreciated both the technical descriptions (esp. those lookup tables) and the historical portions saying where the DX-7 was in relation to other Yamaha FM synths like the 4-operator ones.
I originally got very interested in this when discovering the YM-2151 chip that made 80's arcade game sounds was also found in pro-audio keyboards. They used a very similar YM-2164. This got me to explore the whole DX line including DX-7, DX-9, DX-27S and that keytar that's still popular for bass and talkbox, the DX-100.
Summoning that successful kind of creative, productive, free play state of mind is really difficult in software coding job interviews. There's a lot of back and forth, warming up as well as looking up things and experimenting to reach that flow state. Once you're in it, you know you're in it. You've shipped robust apps thanks to it.
Having to explain that almost instinctive process to a complete stranger who has control over your career and income can really hamper or destroy the ability to get into that groove. I've found it really useful to know about flow, what can get it going and when it's just not happening, and most interviews just aren't set up to encourage it. Csikszentmihalyi wrote a shorter book called "Finding Flow" which speaks of creating situations that bring out the best in others and us.