Abstract: A disk drive of a mass storage subsystem includes areas on a disk surface wherein a vendor-generated defective sector log, a software-generated defective sector log and an alternate sector log are stored. A random access memory (RAM) stores a copy of the defective sector logs. During a seek operation, firmware tests the defective sector logs in RAM to generate the alternate sector log for that cylinder number. During the read or write operation, the alternate sector log is checked before processing the sector to determine if it is a defective sector. If the sector is defective, the head is positioned to another cylinder at a head and sector address read from the alternate sector log.

Abstract: A track on a disk surface of a disk drive is formatted in sectors, each sector having an address portion and a data portion. The disk drive generates a byte clock signal which increments a counter. The counter output signals address a read only memory which generates signals to control the address comparison in the address portion and the reading or writing of data bytes in the data portion of the sector.

Abstract: A track of a disk device is formatted on a single revolution of the disk by using a read only memory (ROM) to store control codes and a random access memory (RAM) to store address field and data field bytes. A DMA controller simultaneously addresses ROM and RAM. Control codes are read into a control first in-first out memory and data codes are read into a data first in-first out memory. The control codes are applied to a decoder whose output signals control cyclic redundancy check and error detection and correction logic as well as the data first in-first out memory. The serial output from both the data first in-first out memory and the cyclic redundancy check logic are written on disk track.