ALL embedded raid controllers are hardware raid. The firmware on the raid controller manages the array, there-for your operating system is not used to manage your array. This is why CPU and Memory recources are not used.
HHMMM...I've heard many people who think that motherboards with onboard RAID have the minimum hardware required for RAID, and can be considered as a "chip with a BIOS" and not real hardware RAIDs. PCI RAID controllers, on the other hand, allow more RAID options e.g RAID 5 and use less CPU resources.
It's not important to know all the answers, as long as you know how to contact someone who does.
Friend of mine has an onboard RAID controller..It's a Promise chipset..ran a series of benchmarks...and then disabled the onboard array..and installed a PCI raid card that was using the same chipset as the onboard raid...the standalone card was faster...albeit not a huge difference...but enough to make note...
Theoretically onboard RAID could be faster..if the chipsets used were controllers that didn't use system resources to make calculations...and that's the difference with onboard RAID...
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.