But - my first computer has the RCA CDP1802 CPU and it indeed has a SEX instruction (SEt X register which is the index for indirect operations - any of the 16 registers can be designated as the X register (or P - program counter). Alas the opcode is not 69. 69 is input from port 1.
My first computer was also RCA CDP1802-based Telmac 1800 - beautiful CPU architecture and easy to learn assembly. Assembly programming has been going downhill ever since.
Edit: Fixed the idiom:
https://www.waywordradio.org/going-downhill/
IC watt mu dither
Had no real micro/mu symbol here
All your resistance are belong to us.
how did you do that?
It's a photoshop, a pretty old and not very good one at that.
Tim