freebsd stable - Aug 2007 - DELL SC430 & ahd0: <Adaptec 39320A Ultra320 SCSI adapter>

Hello
Look. I have a problem with an Integris CathLab System.
It only uses 18GBytes HDD. And nowadays you can figure how difficult is to
get such as discs. Can you tell me a way to limit by Firmware the capacity
of a brand new Disc let says 73 GBytes to just 18GBytes.
By the way, and sure that?s the way Philips works when you order a new disc.
Bye
Raul