ASPI is an interface specification written by Adaptec that provides an application programming interface for standardized communication on a computer bus between a SCSI host adapter and peripherals, whether SCSI or ATAPI. The ASPI layer can also mediate other functions such as burning or ripping of compact discs.
Patin-Couffin may be used in lieu of the ASPI layer for many reasons. First, ASPI must be licensed for use in software not written by a hardware vendor (for example, AnyDVD). Also, ASPI is not Plug and Play compatible, and cannot support USB and Firewire hard drives. Further, ASPI does not allow software to obtain exclusive access to a drive, which is necessary for reliable read/write operations.