## Physical Device Driver Reference

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### PDSK_READPHYSTRACK (64h) - Remarks

This function is used to perform the operations specified on the physical drive in this request. This is similar to the Category 08h commands, except that the I/O is done offset from the beginning of the physical drive instead of from the beginning of the extended volume associated with the unit number (Category 08h).

The Track Layout Table passed in the Parameter Packet is used to determine the sector number, which is passed on to the disk controller for the operation. In cases where the sectors are oddly numbered or are nonconsecutive, this request breaks into n single sector operations and reads one sector at a time. Note also that the device driver does not correctly read a non-512 byte sector if the READ operation would generate a DMA violation error. Applications should be written so that this error does not occur. The sector table that is specified provides information that is used during the READ track operation.