>    pciide0 at pci2 dev 3 function 0: CMD Technology PCI0646 (rev. 0x03)
>    [ ... ]
>    
>    I have no clue if this is a driver issue or the CMD Technology PCI0646
>    simply can not do Ultra-DMA. ISTR it is the latter, though. Which means:
>    there is nothing we could do about it.
> 
> 
> i believe the cmd0646 is the problem;  i recall an email from manuel
> where he couldn't believe they used such a crappy pciide ic...

There are definitely problems with DMA on the 646.  I didn't (quite)
get involved in trying to fix (improve) the solaris driver...

I saw a data sheet which implied that there is a shared data path for the
two channels.
This means that you have problems if you have more than one disk per
controller.  We had 4 controllers with a disk each - until someone
decided sound and integrated video were more important.
With 2 discs per controller (master on each channel) you get horrid
read errors...

    David