Abstract: A method for aging queued commands in a data storage device, wherein a next command is selected from the queued commands based on a combination of an expected access time (EAT) and an incentive term. The incentive term provides for selection of older ones of the queued commands that have larger EATs, instead of younger ones of the queued commands that have smaller EATs. Preferably, the value of the incentive term begins at zero, remains at zero for some number of queue sorts (which are performed before a command is selected for execution), and then increases continuously for some number of queue sorts or indefinitely. Both the incentive term's starting value and the rate at which it increases ate user-selectable parameters, and thus can be used to control service time and throughput in the disk drive's queue.

Abstract: A method for aging queued commands in a data storage device, wherein a next command is selected from the queued commands based on a combination of an expected access time (EAT) and an incentive term. The incentive term provides for selection of older ones of the queued commands that have larger EATs, instead of younger ones of the queued commands that have smaller EATs. Preferably, the value of the incentive term begins at zero, remains at zero for some number of queue sorts (which are performed before a command is selected for execution), and then increases continuously for some number of queue sorts or indefinitely. Both the incentive term's starting value and the rate at which it increases ate user-selectable parameters, and thus can be used to control service time and throughput in the disk drive's queue.

Abstract: Data byte fields and corresponding ECC byte fields to be magnetically recorded as multi-byte records is randomized prior to run-length encoding. The randomized/encoded data is then written. When the randomized/encoded data is read back, the data is first decoded, and then derandomized in a complementary fashion. The randomizing avoids the writing of byte patterns that tend to stress the ability of a head/disk interface to record the data transitions at proper linear track positions. When reading, the complementary derandomizing scheme avoids presenting a repeating pattern of read-errors to the ECC network. Thus, read-errors are not propagated through the read channel. Data is randomized, and subsequently derandomized, in a repeating or pseudo random, complementary sequence for each byte. The complementary randomizing/derandomizing sequence is determined by the count contained in a counter.

Abstract: A multiple transducer disk file format and head addressing/switching control circuitry is shown and described which permits reading all sector identifier (ID) fields during a single rotation of the media using uniformly staggered sectors. This results in an average access latency of one-half revolution of the media and enables the use of maximum or selectively reduced data rates secured by successively storing data in sectors separated by sector fractions which are multiples of the uniform staggering between sectors within a cylinder.

Abstract: Control apparatus is responsive to CPU I/O commands for initiating chained I/O data transfers to cause virtual address translation (VAT) apparatus to translate a first virtual address to be used in the chained data transfer operation and load the translated (resolved) address in an I/O resolved address register reserved (unique) to the commanded I/O device connected to a shared I/O control unit and to repeat such an operation for each I/O device commanded by the CPU to do a data transfer and responsive to a command from the shared control unit indicating that one of the commanded I/O devices is ready for data transfer to become nonresponsive to further CPU I/O commands and cause the VAT to resolve a succession of virtual addresses for the data transfer and to load the resolved addresses into I/O resolved address registers shared for use by all of I/O devices whereby a data transfer operation can commence using the resolved address in the register unique to the I/O device which is first ready for data transfer