The 6502 doesn't have a pipeline, so it's quite easy to count instruction cycles and find out how much time a given piece of code will take. I did this techniq

The 6502 doesn't have a pipeline, so it's quite easy to count instruction cycles and find out how much time a given piece of code will take. I did this technique to bit-bang a serial port back in the day (given two one-bit ports with the CPU doing all the work because the system was too cheap to have an actual UART).