alphaserver 2100 5/250 with promise pci ide controlor - problem with udma

[Francisco José Nina Rente]

Hi all,

I'm trying to install FreeBSD 6.2 with GENERIC on a alphaserver 2100  
5/250 with a promise pdc20269 ide controller.
The objective it's to use one of the scsi disk on the system to boot  
and have the rest of the OS on the two ide disks in RAID 1.
My Problem is:

1- When i boot freebsd i get this messages:

ad0: TIMEOUT - READ_DMA retrying (1 retry left) LBA=0
ad0: TIMEOUT - READ_DMA retrying (0 retries left) LBA=0
ad0: FAILURE - READ_DMA timed out LBA=0
ad1: TIMEOUT - READ_DMA retrying (1 retry left) LBA=0
ad1: TIMEOUT - READ_DMA retrying (0 retries left) LBA=0
ad1: FAILURE - READ_DMA timed out LBA=0

And i can even see the disk geometry in disklabel.

2 - If i set hw.ata.ata_dma=0 on the boot, the messages disappears.  
If i switch from mode PIO4 to udma33 with atacontrol there is no  
problem, at least i can see the disk label and use the disk normally.
If i change to udma66 or udma100 (the maximum that is supported by  
the two disksis udma100) the messages appears again.

I don't want to use less then udma66, of course :( The perfect would  
be udma100 :)
I already try various cable (all 80 conductor cable ), and is the  
always the same thing!.
When i try to use the same promise pdc20269 ide controller in a  
regular x86 box it works normally.

What i need to do to have udma running correctly on this machine?

Another question, what i need to do to force a specify udma level  
(p.e. udma66) on boot?

Anyone can help me, please?

Thank you in advance.

best regards,
FRente