Without plugging something in to the cpu fan header, you will probably not post.
You can plug a 3 pin fan into a 4 pin(pwm) header. The fan will just run at it's rated constant speed.
I tried that but its insanely oose and i dont know if i trust it. is there an adapter i can buy? that takes a 3 pin to a 4pin and if so can you link it?