Just noticed this feature on the P8P67 Deluxe last night. Did not notice it on previous 9128 chips.
HyperDuo lets you "raid" effectively a SSD and an HDD. Some may simplify it as using the SSD as cache but its more complex then that.
here is the marketting brief
Once I get my SSD back from RMA I will test this out and write it up.
Oh.. it says from the 9130 chip.. but it is available on the 9128 as well
I still have to figure out what "threshold" means to in the Marvell BIOS...
Going to be concentrating on RAM the next couple of days, and have to wait for my SSD to come back anyway but hope to have this up shortly afterwards