CentOS - May 2007 - Why new "SCSI" devices in 4.5 kernel?

I've been running CentOS 4.4 on my Thinkpad 600E machine.  Now the new 
2.6.9-55 kernel wants to support the SCSI devices I don't have.

After the 4.4 --> 4.5 update, on the reboot kudzu informed me that it had 
detected my PIIX4 controller.  Well, OK.  That same chipset has been in 
this machine for 10 years, but if the OS wants to re-detected it that's 
fine with me.

FWIW, there's this:

# lspci | grep PIIX4
00:07.0 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ISA (rev 02)
00:07.1 IDE interface: Intel Corporation 82371AB/EB/MB PIIX4 IDE (rev 01)
00:07.2 USB Controller: Intel Corporation 82371AB/EB/MB PIIX4 USB (rev 01)
00:07.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 02)

I also have a new entry auto-added to /etc/modprobe.conf:

alias scsi_hostadapter ata_piix

I also have kernel modules loaded that previously were not used:

ata_piix               14532  0
libata                 99068  1 ata_piix
sd_mod                 15696  0
scsi_mod              112268  2 libata,sd_mod

For completeness I should note that /proc/scsi/scsi shows no attached SCSI 
devices.

Here, finally, is my question: why is my limited system RAM being wasted 
with device drivers I don't need?

It occurs to me that maybe CentOS 4.5 wants to handle my CD-ROM as a SCSI 
device.  Is that done with plain old CD readers?  This Sanyo CRD-S372B is 
far to old to actually write CDs and would probably burst into flames if 
I put a DVD disk into it.

So... any thoughts as to the sudden appearance of this SCSI support?

Thanks.

> So... any thoughts as to the sudden appearance of this SCSI support?
libata was backported?

Steve Snyder wrote:
> It occurs to me that maybe CentOS 4.5 wants to handle my CD-ROM as a SCSI 
> device.  Is that done with plain old CD readers?  This Sanyo CRD-S372B is 
> far to old to actually write CDs and would probably burst into flames if 
> I put a DVD disk into it.
>   

I can't answer the 4.5 specific aspect, but in fact all ATAPI devices 
(CDs,, etc) attached to ATA/IDE use the SCSI command set, unlike IDE/ATA 
hard disks, which use the old WDC1003 'commands'.