Hello Zbigniew,

  ZB> Four. I know, what you mean - not tried to connect the
    > additional HDD to the secondary channel, because I've
    > noticed a strange situation under Linux, which I
    > cannot solve - there was something messed in the way,
    > in which the system "sees" the partition table, when I
    > connected a second HDD to the HPT.

Four channels or four drives (two channels)?  I only see two
(atabus1 and atabus2) in your dmesg.  It seems to me that
NetBSD is handing over wd0 to a drive attached to the intel
(piixide0) adaptor just because it has called the secondary
channel on that atabus0.  In a custom kernel, rather than re
-assigning individual drive device names, you may be able to
provide NetBSD with a gentle nudge by defining atabus0 as
the primary channel on your HPT.

  ZB> But why it isn't set as default option?

I imagine most people don't have their main drive hanging
from atabus>0, in which case it would rarely be an issue.

- Andy Ball.