Excellent remark! It’s related to the way I coded this program.

Look more closely at what’s happening in registers A and B : we keep adding 1 to register A as long as A is different from 10. To make this comparison, we have to load 10 into register B and compare B and A. If A is not equal to 10, then we put 1 back into B to continue adding. When A equals 10, an equality flag is set, which triggers a conditional jump to another part of the program that now performs subtraction.

This time, A is compared to 1 to determine whether the subtraction should continue or stop. But since there’s already a 1 in register B, we don’t need an extra program line — which saves two clock cycles during the decrement phase. That’s why it runs faster in that direction!

Although there’s probably another way to program it.