Gereral Question about the nature of PCI sound cards

So I've done some reading (and as usual, it was inspired by a thread on ocforums hehe) about the fact that using a third-party (excuse me if I'm using the term incorrectly) sound card as opposed to on-board can improve performance when playing games etc.

The reason, as I understand it, is because the sound card takes the work of decoding the sounds in the app away from the CPU, freeing up powe, which can then be applied to creating more FPS, obviously a plus.

If one were to purchase/install a separate sound card though, would it require some type of manual disable of the on-board sound drivers to "signify" to the CPU that it needn't produce the sounds anymore. When you install the drivers for a separate sound card, do they simply take precedence?

As many others, I'm always interesting in any performance gains I can get, especially if they can be achieved simply, as adding a pci card would be.
Could someone educate me a little bit?

There should be an option in the advanced BIOS settings to disable onboard sound. That should do the trick.

well, i would say it really depends on what kind of onboard soundcard you have. my nforce motherboard came with soundstream on the southbridge of the motherboard. while listening to music, the cpu process was like 1-2% and decoding rates were fast. Where as with my older AC97 onboard on an older motherboard, just plain sucked.

you can actually disable the onboard soundcard in your bios, and it does help free up resources which will probably let ur computer load faster. i don't think you need to install drivers in a special way for the new soundcard.. atleast i never did , you don't even really need to remove the old soundcard drivers, if u disable it right, it should disappear from the device manager completly.

Hmm, I'm not sure how to tell what type of onboard I use, but I know that when I installed the chipset drivers from my ASUS CD, I also had to install the AC '97 drivers as well. Though it's a pretty new board (nf4).

I will probably just pop the soundblaster from my old Dell PC into the new rig and see what kind of difference it makes (if any).

@ Korn - What utility do you use to measure the CPU load and decoding rates? I'd like to be able to use something so I can easily compare the before/after numbers (and I'm assuming task manager isn't up to snuff?).

Thanks for the replies so far btw