Ah, the storage saga. Leading up to this P55 launch, almost every motherboard vendor we talked to planned on adding SATA 6 Gb/s connectivity to their boards. The first round of platforms to arrive in our lab actually had Marvell's 6 Gb/s chip on-board. But very quickly, that feature was pulled and the addition of third-gen SATA was called into question for the first round of P55-based motherboards. The rumor was that IDE functionality was problematic, and it'd take a re-spin of the controller to fix. Marvell later came out and confirmed the parallel ATA issues.
Well, now it looks like there will be vendors who integrate 6 Gb/s connectivity right out of the gate, now that the chip has been fixed. ASRock is playing it safe, though, and leaving the controller itself off of its PCB design. Instead, its P55 Deluxe board includes a PCI Express x1 card with Marvell's 88SE9123, two internal SATA ports, and one eSATA port.
We actually applaud this decision. According to Intel storage roadmaps we've seen, "next-gen" SSDs aren't expected until Q2 2010, so the inclusion of 6 Gb/s SATA remains a minor extra at this point. When drives start emerging (assuming they're able to capitalize on the additional throughput), dropping a PCIe card into your P55 platform makes perfect sense.