> > but in fact it DOES depend of udma mode with drives slower that 33MB/s
> > 
> > for example my drive (seagate 20GB) on my VIA MVP3 motherboard with
> > UDMA/33 has 13MB/s transfer speed, with same CPU with intel based
> > motherboard gets 21MB/s (UDMA/33 too), on HPT336 gets 29MB/s
> 
> Then the drives must be too stupid to do simultaneous transfers and disk
> reads.  So, the longer the transfer (of the RAM buffer) takes, the longer
> the drive is "idle" and not reading new data off the disk.

it may be true, but ide interfaces may be unable to saturate IDE bus.
if not there should be no difference between different UDMA/66 controllers