Just got a Simtec IDE card and an ATAPI zip drive for use in a RiscPC.
Upon bootup, the kernel reports:

sd0 at atapibus1 drive 1: <IOMEGA  ZIP 100       ATAPI, , 23.D> type 0
direct removable
sd0(wdc1:1): illegal request
sd0: drive offline

Trying to access /dev/sd0a says 'Device not configured', though the drive 
is briefly accessed the first time.

My kernel is a -current as of last week.

Stephen Borrill