GBC 3 clock mod question

[famiac]

Hello, im new to the forum and sorry for not giving a huge introduction. I have experience modding consoles and i love modding GBCs. I would like to use a 3 position switch to switch between half speed, regular speed, and double speed in a GBC... But i dont know exactly how to wire it. I dont want to take out the current crystal, and i have a 4mhz and 16mhz crystal, and both have 2 pins.

Can someone draw a quick diagram for me on how to wire it? Also, if the same circuit would work on a DMG with 2 and 8 mhz crystals that would be awesome.

Thanks

 

[superben51]

please excuse my crappy paint skills but i think it should look something like this

 

[famiac]

Thanks! but i'm pretty sure there are 4 pins on a 3 position switch...

 

[Mr. Hooker]

that could be a ( on - off - on ) swich, left - 4mh , center - just the 8mh on the bord , right - 16mh, I just have my doubts about leaving the on bord crystal in place. without removing it, I think it will still run at 8mh even if you flip the swich to 4mh.

 

[famiac]

Good point. Will an 8mhz crystal have any effect on game speed? Because there is a .338 differece in clock signal...

 

[Mr. Hooker]

I know you did'nt want to take out the current crystal. but it might be the best way to get it working right.

I would pull the on bord crystal and re-use it if you can as the one for the center with a true 3 way swich with 4mh, standard, 16mh, so only 1 can work at a time.

Will an 8mhz crystal have any effect on game speed? Because there is a .338 differece in clock signal...

unless someone who has done a mod just like this before tell's you differently, I think testing it for yourself to see if you like the gameplay of it would be your best bet.

edit: sorry for no diagram, guess I could drawl it on paper, and use my webcam to post it.... meh, a thousand word's outweighs a picture.

 

[famiac]

Haha thanks man. But a diagram would be incredibly useful since i have no idea where to wire things up on a 4 pin oscillator (crystals have no polarity but the 4 pins are confusing.) Im so glad people on forums are so helpful.

 

[vskid3]

Good point. Will an 8mhz crystal have any effect on game speed? Because there is a .338 differece in clock signal...

Its only about a 5% difference. You might be able to tell by the sounds being slightly different, but overall gameplay should be almost identical.

 

[famiac]

I would like to use the original crystal but i dont know how to wire it.

 

[famiac]

Figured it out, ill use a DIP switch with 3 switches.