NES / famicom controller cord length mod

I discovered that the original nes / famicom control pad pcb the controller stops working once you make the cords longer than a certain length. In the dogbone controller pcb they fixed this, here's the fix:



3.6k ohm between vcc and cup
3.6k ohm between out 0 and vcc

Anyone have an idea why this fixes it and allows you to use your gamepad with as many extension cables as you desire?

You'll probably still end up with a limitation at somewhere around 18 meters due to speed of electrons in copper (about lightspeed÷3) and the synchronous nature of the controller reads (so an additional ÷2).

If I were to take an arbitrary guess, it'd be that the pullup in the NES/famicom is "only" 10kiloohms, which may not allow enough current through to handle the amount of capacitive load imposed by the extenders.

I think the problem is capacity of the cables. Decreasing R decrease the time factor R*C it takes for the state to change within the cable.

The only way to do it right is add buffers on the inputs and outputs. We have done this to extend the cable to over 100ft through different wire.