[Someone]

”It has four main registers R1-R4 and nine extra registers R5-R13“

I found that ‘4’ a weird choice for a ternary computer, until I read that R1 is special.

Register-to-register moves always involve R1. There are 12 such moves into R1 and 12 out of R1. That leaves 3 trit patterns in a 3-trit value for “increment R1”, “decrement R1” and “NOP”.

Also, this architecture doesn’t allow reading data from, or writing data to memory. The memory only is there for storing. programs. So, it’s almost as if this has one register, 12 words of data memory and 729 words of program memory.

Weird, but economical on the hardware, I guess, so it keeps the cost and amount of work down. Also, there’s room for extension commands, so the above may change.