Enabling atapicam -> Interrupt storm during boot

Hi,

if I enable "device atapicam", the kernel hangs during bootup, right
after probing the ATA devices. The last message to be seen is:

    Interrupt storm detected on device "irq20: atapci0" [...]

(or similar, don't have the machine next to me right now).
After this, the machine seems to be dead, only reset helps.

I tried the same thing with a GENERIC kernel and adding just atapicam.
Same results.

This was with a recent RELENG_5 kernel. Using a kernel built from
-CURRENT sources (CTM from few days ago) the interrupt storm message
does not appear, but the system deadlocks at the same point.

System is an amd64, Via KT800 chipset, disk and CDR on SATA.

I don't have experience in debugging these things, but I'm happily
ready to do any debugging that may help or test patches. The machine
isn't really being used right now ;-)

TIA!
- D.

P.S.: Seems like there are related PRs: kern/74272 and 73675.