Specifications

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5.1.4 Error Map
All drives are scanned for hard etTon during the manufACturing process. AU hard errors (media defects) are logged
and an error map is attached to each drive. Each defed listed contains the foUowing information
a. Track number
b. Head number
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I c. Byte count accurate to ± 4-bytes (Indicates the defective bytes as a location from physical index)
d. Length of defect in bits
The error map accompanying each drive will typically provide the locations of more hard errors than will be
detected by the user system. There are situations, however, where a magnetic anomaly or extra defects caused by
improper handling may cause an error that is unique to a particular format or bit pattern. Such a flaw may present
itself
as a hard error, in addition to those reported on the error map. In the event this situation occurs, it is recom-
mended that the defect be added to the error map and mapped out. .
5.1.5 Uaer Error Mapping
Occasionally, errors shown on the error map~ supplied with the drive will not show up as errors in the user's
system.
Similarly, the user may find hard errors In addition to those on the error map dUring the user's functional
tests
The recommended method of mapping is to aeate a defect directory at cylinder 00. This directory should include
the locations of all defective areas, as well as alternate track assignments for those areas.
5.2 ERROR ACCEPTANCE CRITERIA
The drive, as received from the factory. wUl'meet the following error criteria:
a.
No disk will have more than ten defective tracks. Of these ten tracks. no more than three will contain
multiple defects. Additionally, track
00 of ,all heads Is g~anteed to be error free.
b. Errors
separated by less than 20 bytes from beginning to end. or less, 20 bytes long, are considered
one error.
5.3 SYSTEM GENERATED ERRORS·
It
should be noted that errors may also be present as a result of system electrical noise, marginal timing conditions,
ground loops in the dc power distribution cable. electro-magnetic interference, radio frequency interference, etc.
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