Conflict detection for queued command handling in disk drive controller
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United States of America Patent
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Dec 3, 2002
Grant Date -
N/A
app pub date -
Apr 28, 2000
filing date -
Apr 28, 2000
priority date (Note) -
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status (Latency Note)
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Abstract
A conflict detection method for a disk drive controller is used to handle a conflict potentially occurring if the execution sequence of queued commands sent from a host to a controller is reordered to optimize disk drive transfers. The conflict detection method determines if there is an address range overlap between two queued commands. If an overlap exists, a conflict flag is set. The controller microprocessor utilizes this flag to restrict command reordering and prevent a conflict from producing erroneous data. Conflict detection and command reordering restriction are facilitated by a queued command RAM and a command FIFO. The queued command RAM stores command parameters indexed by command tag values. These parameters include command direction (read or write), LBA, block count, a valid flag and a conflict flag. The conflict detection method compares the address range of a new command with the address range of valid commands in the command RAM to determine range overlaps. If an overlap exists with a new write command, the conflict flag is set for both the write command and the overlapping commands in the queued command RAM. The microprocessor accesses the queued command RAM to determine which chronologically ordered commands in the FIFO must be executed in sequence.
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