SIGH .... I hope we can fix this in the next release ...

Adaptec 1542 controllers use a make believe geometry of 64 heads and 32
sectors yielding a cylinder of 1Meg.  You need to get the disk capacity
in sectors and divide it by 64*32 sectors to get the number of
cylinders.  This is the number that YOU MUST tell NETBSD when it asks
about the disk geometry.   Otherwise all bets are off that the boot
program can find the OS.  This is especially true if you have more than
one OS on your disk.