[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Interfaces and Configuration | Small Computer Systems Interface (SCSI) | SCSI Host Adapters ]

Protocol Support

Obviously, a key issue in selecting a host adapter is support for the particular transfer modes and feature sets that you want to use. The host adapter must be able to support all of the protocols that you want to use on the bus. If you want to use wide SCSI, the adapter must support 16-bit operation; if you want to use Ultra160 SCSI hard disks, your host adapter must be capable of supporting this speed. Nothing too surprising here.

Typically, host adapters are backwards compatible with older devices, so you can run a newer drive on an older, slower host adapter--you just give up some of the performance of the drive in doing so. Similarly, newer host adapters will support older, slower devices, providing that they are properly configured. See this page for more on compatibility between different SCSI flavors.

Of course, host adapters that support faster transfer modes are generally more expensive than ones that only support slower devices. Remember though, that if you purchase a cheaper, less capable host adapter, you will be limiting your expansion capabilities should you later decide that you do want to use the faster mode. Whether the more capable host adapter is worth the extra money depends on your situation and the chances that you will want or need to upgrade in the future.

Next: Signaling Type Support (SE, HVD, LVD)

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