These headers and trailers are typically the same or similar for each transfer. Therefore, there may be a single copy of these messages but multiple data buffers. Spanned commands can be implemented in system hardware due to address-alignment requirements. As a result, spanned commands are potentially faster to run. Gathered write commands are not able to handle read requests.
Spanned commands can handle both read and write requests.
Gathered write commands can be initiated only on the process level, but spanned commands can be initiated on either the process or interrupt level. Be attempting a write. This interface allows the IDE adapter device driver to perform the gathered write commands in both software or hardware as long as the adapter supports this capability. The gathered write command facility is optional for both the IDE device driver and the IDE adapter device driver. Attempting a gathered write command to a IDE adapter device driver that does not support gathered write can cause a system crash.