G - Physics – 11 – B
Patent
G - Physics
11
B
352/21.21, 352/1
G11B 5/09 (2006.01) G11B 20/18 (2006.01)
Patent
CA 1246210
REMAPPING TECHNIQUE FOR HANDLING MEDIA DEFECTS IN A DISC DRIVE SYSTEM ABSTRACT OF THE DISCLOSURE A remapping technique for handling media defects in a disc drive system is disclosed. Each surface on each disc is divided into a number of tracks with the corresponding track on each disc defining a cylinder. Each surface in further divided into a plurality of sectors. Each sector is each cylinder not having a defect is assigned a logical address in sequential order such that as the discs rotate and as the head address increments within a cylinder, each succeeding defect-free sector within that cylinder has a logical address which is related to the logical address of the preceeding defect-free sector. Defective sectors are labelled with an appropriate unique pattern in their headers so that they can be identified and distinguished from logical address numbers. A predetermined number of sectors at the end of each cylinder are allocated as spare, the number of spares being at least as large as the number of potentially defective sectors in a cylinder and the number of spares to which logical addresses are assigned being equal to the number of non-spare sectors which are defective. In using the technique, each defect- free sector in a cylinder is located and assigned its logical address. In transferring information, the header address of a sector in a cylinder is compared with the logical address expected at that location. If the addresses compare, the data at that sector is transferred. If the addresses do not compare the header address at the next physical sector is compared with the expected address. The procedure is repeated until the address at a physical sector compares with the logical expected address. However, if the sequence of mis-compares exceeds a predetermined number, the sequencing operation is terminated and an error signal generated. The technique eliminates moving the heads radially inward or radially outward to spare tracks allocated for data belonging in defective sectors as in most prior art systems. - 2 -
454835
Data General Corporation
Macrae & Co.
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