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In computers, ASPI is a standard SCSI software interface that acts as a liaison between host adapters and SCSI device drivers. ASPI enables host adapters and device drivers to share a single SCSI hardware interface. Because ASPI works between the hardware components on a SCSI bus, it is usually referred to as the ASPI layer.
Components of the ASPI layer include:
- ASPI manager: A software module that provides an interface between ASPI modules, a host adapter board, and the SCSI devices connected to the adapter. A single ASPI manager can handle multiple I/O requests from multiple ASPI modules. ASPI managers are written for a specific operating system (such as NetWare, OS/2, UNIX and others) and a specific family of host adapter boards.
- ASPI modules: Device-level code specific to a particular kind of SCSI device that communicates with the ASPI manager.
Historical origins of the ASPI layer:
In the early days of CD-ROM, every manufacturer had their own proprietary interface and connections to the host adapter card. Standard interfaces, ASPI and CAM (which will operate ASPI devices and is functionally equivalent for Windows platforms) were eventually devised, and manufacturers of SCSI devices either conformed to the standard or exited the market. The situation with IDE devices was similar, but the standard that was developed for them (ATAPI) made them look to the system like SCSI and allowed them to work through ASPI. For that reason, a computer's IDE adapter and devices may be listed under the SCSI controls.
Sources: Adaptec, Mike Richter. An excellent reference for Windows users that was not cited in this writeup can be found at http://www.ncf.carleton.ca/~aa571/aspi.htm