Board Thread:Suggestions and Ideas/@comment-24191375-20140630181109/@comment-5334617-20140630203305

Here's an example that might help you understand.

I have calculated that PTC can execute the instruction  about 1115 times a second.

The NES processor runs at approx. 1.7MHz, the Gameboy processor runs at approx. 4MHz. Now, the rate at which instructions are executed is not the same as the clock speed, I don't have precise details, but I don't think it's as much as a factor of 10 difference. This means the NES will execute a single increment instruction 170 times faster than PTC could, and the Gameboy, 400 times faster.

And the emulator not only has to do the actual increment, it first has to fetch the instruction from memory, analyze it to see if it is an increment instruction, then find out which register gets incremented. The PC example had the instruction and variable already known, so that's much more overhead again.

And that's not even taking into account the side-effects of the increment on the status register, or many many other considerations.