ATAng vs Aladdin chipset

ASUS P5A or P5AB (one of each now) - won't boot without setting
hw.ata.ata_dma=0.  GEOM recognizes the drive itself but then the reads
of the disklabels fail with a message that I can't find in the source,
about a DMA failure.  System then prompts to mount root and nothing I
type works.  I see looking at the list archive that I'm not the only 
one with this problem.  The message appears 3 times per drive with some 
seconds between, implying to me that it is (at least) a missing interrupt
(or completely missing operation?).

If anyone wants I could take the trouble to set up a serial console
and capture the output.  I suspect that is already done somewhere
though.

Approx same cvsup time works fine in my laptop running ICH3 chipset.
Then again, Intel != Acer :-)

At least I figured out a bypass easily...  Makes "make world" lots
slower but at least works.

Other (unrelated?) minor problem in past (don't know if it's still there); 
acpi timer doesn't work right on this chipset either (ran clock at approx 
double rate with lots of "went backwards" messages).  Appears better now at 
least on one example (non-ASUS board, though) - at least ntp is happy.

-- Pete