PF21 has 2 RAID controllers. One is ICH6R and the other is SIS180.
On-chip IDE device -> On-chip Serial ATA -> Enable / Disable is for ICH6R RAID controller.
Onboard Device -> Onboard SATA device -> Enable / Disable is for SiS180 RAID controller.

It's a limitation if you enable ICH6R, SiS180 RAID & boot ROM at the same time. Since the upper memory allocation is not enough for these 3 ROMs, the temporal solution is disabling "USB K/B & mouse support" items in BIOS (if they are only for Legacy MS-DOS support). If you disable those USB items, you can use below combinations.
 
- SiS180 RAID + ICH6R SATA w/o RAID + LAN boot ROM
- SiS180 RAID + LAN boot ROM
- ICH6R w/ RAID + LAN boot ROM
- SiS180 RAID + ICH6R RAID

The PF 21 only support DDR2 400/533 memory. We suggest you use DDR2 400/533 and try to use DDR2 667 but it may detect to DDR2 533)in this MB. DDR2 800 should not be supported in this MB.