Seagate Technology Incorporated

Swee Kieong Choo

Beng Wee Quak

Teck Khoon Lim

Myint Ngwe

Wei Loon Ng

YongPeng Chng

Choon Wei Ng

WeiLoon Ng

Song Wee Teo

HuaYuan Chen

Jack Ming Teng

Kwee Teck Say

Wing Hung Chan

Kok Hoe Chia

Chwee Fern Ee

Hwee Peng Teo

A method to improve drive read performance in a disc drive includes powering-up a disk drive, reading reassigned sectors data from a reassign spare pool, and storing the reassigned sectors data in a reassigned cache segment. This method also includes initiating a read request, detecting a reassigned sector within the read request, and determining whether the requested sector can be located in the reassignment cache. If the reassigned sectors are found in the cache, then the method includes transferring the reassigned sector data from the reassignment cache to the read buffer or directly to the requesting host computer. If the reassigned sectors are not found in the cache, then the method includes seeking to the reassignment spare pool to fetch as much reassigned sectors data as the reassignment cache can hold. In another embodiment, the reassigned sectors data stored in a reassignment cache segment is located in a buffer.

Caching data from a pool reassigned disk sectors

A method and apparatus for virtually expanding the rapid-access memory space of a device employing time-critical software modules and having various modes of operation. Each of the modes of operation of the device is identified. For each mode of operation, the time-critical software modules used during the mode are identified. The software modules used during all modes of operation are permanently stored in rapid-access memory. However, a software module that is used only during a particular mode of operation is loaded into the rapid-access memory unit only upon entry into the mode of operation in which it is used. The software module is loaded into a region of memory occupied by another software module not utilized during the particular mode of operation being entered.

Virtual expansion of program RAM size

A method and apparatus for detecting and recovering from head instability in a magneto-resistive (MR) transducer head of a disc-drive system. A head-instability-recovery circuit is described for use in disc drive to recover from a head-instability condition of an MR transducer head. This circuit includes a controller and a current source that supplies current to the MR head. The current source is controlled to supply a nominal amount of current to the MR head when operating in a normal mode, and to supply one or more current bursts having a current above the nominal supply current in order to recover from the head-instability condition. Also described is a method for recovering from a transducer-instability condition of an MR transducer of a disc drive, including detecting a situation that indicates a head-instability-recovery operation is desired, and performing the head-instability-recovery operation.

Self-diagnostic MR head recovery

A logical-to-physical head map is built upon each power up of a disc drive. After powering the controller and disc drive spindle motor, a bias current is iteratively supplied to the read heads in succession. A representation of the voltage across each read head is stored in a fault register for comparison to a threshold and a &ldquo;good&rdquo; or &ldquo;bad&rdquo; fault status is stored for each head. A logical-to-physical head map is defined based on the number of logical heads, which in turn is based on the disc drive serial number. Each of the logical heads in the logical-to-physical head map is associated to a respective one of the heads having a &ldquo;good&rdquo; fault status to construct the logical-to-physical head map in the controller memory.

Disc drive power-up process including head mapping

The present invention pertains to an apparatus and method for recording data in a variable bit density disc drive. The disc drive includes a recording surfaces, each having a corresponding head for recording data on the recording surface. At least one head is operated at a different recording frequency from the other heads, creating a variable bit density for the different recording surfaces. The combination of head recording frequencies is determined following an error testing operation and a unique physdisc lookup table is created based on the determined recording frequencies. The physdisc lookup table is used to allocate data sectors and to convert between logical and physical block addresses.

Implementation of variable bit density recording in storage disc drives

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Singapore, Singapore

Swee Kieong Choo