ASPI

3/23/2002

ASPI (Adaptec/Advanced SCSI Packet Interface). ASPI is software designed to manage communication between high speed data devices and PC OSes. It consists of an ASPI layer in the user's environment that handles ASPI function calls, and one or more device specific drivers. ASPI was originally designed by Adaptec for use with SCSI CDROMs, Tape drives,etc. It was later expanded by Microsoft to provide similar services for IDE devices. It is not used for accessing hard disks which are handled directly by SCSI/IDE controllers. ASPI is used by or usable with MDSOS, Windows in all its incarnations, Netware and OS/2. It is not used by Apple, Unix or Linux. ASPI on Windows NT, 2000, and XP is relabeled as "SCSI pass-through". It may not work with all ASPI applications. Some people install Adaptec's ASPI or an ASPI implementation from some other vendor.

Even within the ASPI using OSes, there may be alternative interfaces including the Common Access Method (CAM) and NT Pass through. but they are not widely used.

In principle, ASPI provides a common, device independent, method of accessing hardware. In practice, the situation is a bit different. There is no formal public ASPI specification. The Interface used by Adaptec SCSI drivers is the de facto standard. However Adaptec and Microsoft have had a falling out that precludes distribution of Adaptec ASPI drivers with Windows software. Microsoft distributed drivers (if any) are reported to be decidedly less reliable. Moreover, while Adaptec makes its drivers available for download, the installation software checks for the existence of (Adaptec?) SCSI hardware before permitting installation. To further exacerbate the confusion a full ASPI installation usually requires four or five drivers which may differ with OS version. All the drivers must be compatible. "Legacy" drivers remaining in place after an upgrade can cause trouble. If Adaptec drivers are to be used with IDE devices, it may be necessary to look into the ForceASPI program and/or to install a fictitious Adaptec 4940 controller in the Windows configuration.

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