Command Specifications
3-88
C141-C010
Bit
Byte
7
6
5
4
3
2
1
0
0
Cylinder No. (MSB)
1
Cylinder No.
2
Cylinder No. (LSB)
3
Head No.
4
Physical sector No. of defective block (MSB)
5
Physical sector No. of defective block
6
Physical sector No. of defective block
7
Physical sector No. of defective block (LSB)
Figure 3.25 Defect descriptor: physical sector address format
•
Cautions in specifying the D list
The P List, containing defect position information, is always recorded on the IDD when it is shipped
from the factory. Also, information on defect positions for which alternate block processing has
been implemented during operation are recorded as the G List. The function which specifies defect
position information as the D List when the FORMAT UNIT command is executed, is prepared
mainly to specify initial defect position information of the disk media which does not have the P List
recorded on it. In the IDD, by specifying use of the P List and G List, advance notice of the defect
positions can be specified during initialization, so ordinarily, it is not necessary to use the D List.
When the D List is used for the IDD, caution should be exercised in the follow points.
1.
The maximum number of defective sectors (total amount of 'sector slip' and 'alternate sectors')
are calculated per :
a)
Current condition of reallocated sectors:
(how many Slip Sectors have been allocated? and so Alternate Sectors? Since Defect table
entry for Slip and Alternate are different size.)
b) The maximum size of Defect Management Table (Fixed value)
c)
Current allocation condition of 'sector slip'
(i.e. Up to 16 consecutive Slip Sector can be controlled by 1 Slip Defect entry. So the
necessary table size are varied not only the number of Defects but also the number of
consecutive Slips.)
Consequently, the concrete Defect numbers cannot be described though the IDD guarantees
12,000
Slip Sectors and 3,000 Alternate Sectors at minimum. If defect processing which
exceeds this limit is specified in the FORMAT UNIT command, that command is terminated
with a CHECK CONDITION status (HARDWARE ERROR [=4] / No defect spare location
available [=32-00]).
2.
A defect descriptor specified as the D List are received normally if the specified defect position
information is within a range which does not exceed the disk drive’s physical boundaries (User
Space), and is recorded as the G List, but formatting processing is executed only for the User
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