: n represents a logical data block number
: Defective sector
: Unused spare sector
Figure 3.7 Alternate block allocation by FORMAT UNIT command
If the data block verifying operation (certification) is not permitted (DCRT flag = 0) in the FORMAT UNIT command, the IDD checks all initialized logical data blocks by reading them out after the above alternate block allocation is made to initialize (format) the disk. If a defective data block is detected during the check, the IDD generates the C list for defect location information and allocates the alternate block to the defective data block. This alternate block allocation is made by means of alternate sector treatment only like processing by the REASSIGN BLOCKS command even if unused spare sectors exists in the same cylinder.
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