hdd=ide-scsi (instead of hdd=scsi)
and
omitting hdd
have no effect

here is the output of uname -r
2.6.5

and output of cat /proc/scsi/scsi
Attached devices:
Host scsi0 Channel: 00 Id: 00 Lun: 00
Vendor PLEXTOR Model: CD-R PREMIUM Rev: 1.02
Type: CD-ROM ANSI SCSI revision: 02

Host scsi1 Channel: 00 Id:00 Lun:00
Vendor: IOMEGA Model: ZIP 100 Rev: 0.3H
Type: Direct-Access ANSI SCSI revision: ffffffff

-ishwar