Problems burning CDs with ASUS P5B-E

Hi!

I'm having some problems burning CDs and DVDs with -current on a 
new ASUS P5B-E board with an Intel Core 2 Duo. The IDE DVD drive, a Plextor 
PX708A is connected to the JMicron JMB363 controller.

First of all, there's a problem detecting the atapicam based cd0 device. As 
long as hw.ata.atapi_dma is set to 1, the boot hangs while the kernel 
searches for the device. Many commands time out like:

(probe0:ata4:0:0:0): xpt_schedule
(probe0:ata4:0:0:0): xpt_setup_ccb
(probe0:ata4:0:0:0): probestart
(probe0:ata4:0:0:0): xpt_action
(probe0:ata4:0:0:0): INQUIRY. CDB: 12 1 80 0 ff 0
atapi_action: hcb_at_0xc4a47c80: 12 1 80 0 ff 0
(noperiph:ata4:0:-1:-1): xpt_async
(noperiph:ata4:0:0:0): xpt_compile_path
(noperiph:ata4:0:0:0): xpt_release_path
acd0: FAILURE - INQUIRY timed out
atapi_cb: hcb_at_0xc4a47c80 sense = 00: sk = 0
acd0: cmd INQUIRY status 00 result 05 error 00
(probe0:ata4:0:0:0): xpt_done
(probe0:ata4:0:0:0): camisr
(probe0:ata4:0:0:0): probedone
(probe0:ata4:0:0:0): xpt_action
(probe0:ata4:0:0:0): INQUIRY. CDB: 12 1 80 0 ff 0
atapi_action: hcb_at_0xc4a47c40: 12 1 80 0 ff 0
acd0: WARNING - TEST_UNIT_READY taskqueue timeout - completing request 
directly
(noperiph:ata4:0:-1:-1): xpt_async
(noperiph:ata4:0:0:0): xpt_compile_path
(noperiph:ata4:0:0:0): xpt_release_path
acd0: FAILURE - INQUIRY timed out
atapi_cb: hcb_at_0xc4a47c40 sense = 00: sk = 0
acd0: cmd INQUIRY status 00 result 05 error 00
(probe0:ata4:0:0:0): xpt_done

Nevertheless, after about 20 minutes both devices, an acd0 and a cd0 are 
recognized. I can mount a CD using both acd0 and cd0 and reading from the CD 
is no problem. But when I try to burn a CD or DVD with burncd or cdrecord, 
after a while the drive's LED stops blinking and the process then hangs 
indefinitly.

If I turn dma off (hw.ata.atapi_dma="0" setting in loader.conf), the drives 
are correctly detected and there are no hangs (no timeouts) during boot. 
Mounting and reading from the CD is no problem, but burning doesn't work 
either :-(.

Any ideas?

Thanks in advance,
Christian.