Yeah, that is weird. My motherboard has the Realtek ALC889A codec on it and my mic works fine. In fact I've had people in game ask me to lower my mic volume a bit. All I did was set my mic volume (recordding devices) around 80% and set my mic boost to 20%.
Did you install the driver only or the entire realtek audio manager? If you installed the audio manager, I'd makes sure all the settings look correct in there. If you haven't installed the audio manager, you may want to give it a try. I adjusted all my settings in the realtek audio manager.