Hard Disk Drive Command Overlapping

Command overlapping allows a hard disk drive to release the bus before the command execution is completed in order to allow the second hard disk drive, which is on the same bus, to receive a command or to transfer/receive the data. Support of command overlapping, first appeared in ATA/ATAPI-4 version, allows efficient parallelizing the work of the hard disk drives, which are on the same data bus. The usage of the given technology provides the hard disk drive support and the driver usage of the following commands:

• NOP (with non-zero parameter)
• READ DMA QUEUED
• READ DMA QUEUED EXT
• SERVICE
• WRITE DMA QUEUED
• WRITE DMA QUEUED EXT
• WRITE DMA QUEUED FUA EXT