8-STABLE ahci fails to attach, does not fallback on ataahci

Hi lists,
I gave ATA_CAM a try last night and believe I have a similar setup 
(crippled hardware) in my laptop as Doug Barton's, although my 
controller is ICH6M.  Nonetheless, ahci detects my controller and tries 
to attach and fails (returns 6).  No ada nodes are created and the boot 
process halts trying to find a root mount.  Verbose booting reveals 
nothing special.  Anything else I can do to try to reveal the problem?

I tried modular ATA with the following:

device atacore
device atapci
device ataahci
device ataintel

device ahci

 From reading the lists more thoroughly, I now have the impression that 
either ahci or ataahci are necessary and not both.  If I remove 'device 
ahci' then 8-STABLE boots normally.  However, I would think that if ahci 
failed to attach then the kernel should fallback on ataahci.  If GENERIC 
included both ahci and ataahci, then I would never be able to boot 
FreeBSD let alone install it.

`uname -a`
FreeBSD LIGHTBULB.LOCAL 8.0-STABLE FreeBSD 8.0-STABLE #4: Thu Dec 24
02:40:23 EST 2009
nslay_at_LIGHTBULB.LOCAL:/usr/obj/usr/src/sys/LIGHTBULB  i386

Here's what appears in my dmesg:
atapci0: <Intel ICH6M SATA150 controller> port
0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0x18c0-0x18cf at device 31.2 on pci0

and the result of `pciconf -lv`
atapci0_at_pci0:0:31:2:    class=0x010180 card=0x056a1014 chip=0x26538086
rev=0x03 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = '82801FBM (ICH6M) SATA Controller'
    class      = mass storage
    subclass   = ATA

the kernel was built from 8-STABLE tree as of last night.

Best Regards,
Nathan Lay