Hi,
I've just commited an ahci driver. Works fine for me on Intel 63xxESB AHCI
controller:
ahcisata0 at pci0 dev 31 function 2: Intel 63xxESB AHCI Serial ATA Controller
ahcisata0: AHCI revision 1.0, 6 ports, 32 command slots, features 0xc6226000
ahcisata0: interrupting at ioapic0 pin 19 (irq 10)
atabus0 at ahcisata0 channel 0
atabus1 at ahcisata0 channel 1
atabus2 at ahcisata0 channel 2
atabus3 at ahcisata0 channel 3
atabus4 at ahcisata0 channel 4
atabus5 at ahcisata0 channel 5
ahcisata0 port 0: device present, speed: 3.0GB/s
ahcisata0 port 2: device present, speed: 3.0GB/s
wd0 at atabus0 drive 0: <Hitachi HDS721616PLA380>
wd0: drive supports 16-sector PIO transfers, LBA48 addressing
wd0: 153 GB, 319120 cyl, 16 head, 63 sec, 512 bytes/sect x 321672960 sectors
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
wd0(ahcisata0:0:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) (using DMA)
wd1 at atabus2 drive 0: <Hitachi HDS721616PLA380>
wd1: drive supports 16-sector PIO transfers, LBA48 addressing
wd1: 153 GB, 319120 cyl, 16 head, 63 sec, 512 bytes/sect x 321672960 sectors
wd1: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
wd1(ahcisata0:2:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) (using DMA)

Note that this driver will only attach if the controller is in AHCI mode
(there's usually a BIOS option for this); if it's in compat mode it'll
be handled by piixide as before.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--