I did a little searching and came up with not to much. I have a original nes controller that I want to add turbo switches in and I am not sure how to do this. I may just break down and buy a joycard or something but third party controllers always feel odd and i hate the nes advantage and max. They are just clunkie.
Look for "autofire circuit" or "turbo circuits" on google. From what I've read, they are generally made with a 555 IC. There are ICS that are essentially multiple 555 ICs in a single package (556 for 2 and 558 for 4 IIRC). Also, you should "tune" your design to about 16 pulsations/sec because that's the top speed that a human can achieve, so higher than that can give problems in some games.
Regards.
Thanks for the info that was relay helpful.
Instead of hacking your controller, try to get a Turbo Blaster (http://www.youtube.com/watch?v=nAtw25Fxh8I). It's an adapter that comes between the console and the controller, and you can use it to set autofire to A or B. It even allows to set the rate of autofire.
I have one myself, works great. A bit hard to come by, but a very cool thing. And you can use it with all controllers using the NES controller ports, I'm using it on an AV Famicom.
I would get one but they are on average about $20-50 depending on market. i am looking for a cheaper solution. Also I like to tinker with things. its a hobble.
Russian "Dendy" consoles turbo had 6Hz frequency (6 times per sec).
555 timer instructions for mouse:
http://makezine.com/projects/adding-auto-fire-to-a-computer-mouse-555-timer/ (http://makezine.com/projects/adding-auto-fire-to-a-computer-mouse-555-timer/)