NEC CP/M-86 - Page 222

Physical Format of Hard Disks
J-4
ERROR MAP
The error map (cylinder 0, sectors 0 and 12) is used to reallocate the next normal
track in place of a bad track. Sector 0 is the error map. Sector 12 is the back-up error
map.
The map is formatted as shown in Figure J-2. Each bit corresponds to a track on the
disk.
o 5
6 7 8
188 255
I I I I
I I I I
EIRIMIAIP 6.
I I I I
I I I I
Figure J-2 Error Map
NOC
C
IC I C' I I I I I I I
I I I I I I I I I I
# : # : # I ERROR BIT MAP
o III 2: I : I : : : I
I ,
,
.......
.......
/
........
/
........
/
~
t
~ t
t
: t
: t I
t
,
I
I I
O~
1
2
:3
: 4 :
5
MSB
............
: t
:6
1 = bad track
.............
: t
:7
LSB
o
= normal track
L Number of Cylinders
C#O - C#180: Cylinder No. 0-180
to - t7: Track No. 0-7
To reduce seek time, the system uses the track that immediately follows the bad
track for the reallocation. Figure J-3 demonstrates track reallocation.
UNU:EDI