ICH5 SATA RAID boot failure on -CURRENT

The system in question is a Supermicro Superserver 5013CT
(http://www.supermicro.com/PRODUCT/SUPERServer/SuperServer5013C-T.htm) which
uses the Intel ICH5 chipset for it's RAID.

Despite there apparently being ICH5 SATA support in both -STABLE and
-CURRENT as of last summer, I cannot get any version of FreeBSD to install
onto these drives while the ICH5 controller is configured for SATA RAID.

In the motherboard BIOS there are several configuration settings for the
SATA mode. First, they can be configured as RAID (either level 0 or 1),
which is how I'd like to run. Next, there are two different "legacy" modes
(one, where SATA takes the place of the PATA drives, and another where PATA
and SATA both run side by side).

If I run in one of the legacy modes I am able to boot, and 5.2-RC1 detects
and is able to install to the disks. However, RAID cannot be enabled in
legacy mode so it is not overly useful.

If I enable RAID (and it doesn't matter whether the 2 disks are configured
as striped, mirrored, or with no RAID volumes defined at all) then the
installer hangs at the boot loader on the 5.2-RC1 install CD.

The error is:
-----
BTX loader 1.00 BTX version is 1.01
Console internal video/keyboard
BIOS CD is cd0
BIOS drive A: is disk0

int=0000000d err=00000000 efl=00030046 eip=00009066
eax=000000b8 ebx=000028280 ecx=0000000 edx=000008ee
esi=00009701 edi=00001f98 ebp=00000000 esp=00001800
cs=0000 ds=0000 fs=0000 gs=0000 ss=0000

es:eip 0f 01 1e d6 96 0f 01 16-d0 96 0f 20 c0 66 83 c8
01 0f 22 c0 ea 7f 90 08-00 31 c9 b1 10 8e d1 b1
ss:esp=0a 69 6e 74 3d 30 30 30-30 30 30 30 64 20 20 65
72 72 3d 30 30 30 30 30 - 30 30 30 20 20 65 66 6c

BTX halted
-----

The numbers appear identical through reboots.

I get the same effect if I boot from a -CURRENT snapshot from 1217 as well.

If I boot from a 4-STABLE snapshot from 1202 then I don't get any errors on
bootup, but once I get to sysinstall it is not able to detect any disks to
install to.

I'm a bit stumped, as I've seen newsgroup/mailing list posts saying that
ICH5 is supported, I can see that code is supposedly there to support it if
I look in CVS, and I've seen comments from Soren regarding it's support, and
it kind of works if I use legacy mode. 

I've submitted a PR (still waiting for the email with the PR#), but I'm also
posting it here in case anyone using them has managed to get them to work.

Thanks

---
Nicholas Paufler
Systems Administrator
The Internet Centre