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I B M 3 740 F o r m a t
T h e r e a r e t w o I B M 3 7 4 0 f o r m a t s ; D a t a S e t L a b e l a n d T r a c k .
c o m p a t i b l e t o b o t h f o r m a t s .
T r a c k 0 0 c o n t a i n s o n l y D a t a S e t L a b e l s t h a t i d e n t i f y t h e t y p e o f i n f o r m a t i o n s t o r e d
in t r a c k s 01 t h r o u g h 7 6.
e a c h c o n t a i n i n g 128 d a t a b y t e s .
o v e r f l o w to o t h e r o n - l i n e d i s k d r i v e s .
n o r m a l l y u s e d .
T r a c k 74 a n d 75 a r e r e s e r v e d as s p a r e s to b e u s e d w h e n o t h e r
t r a c k s b e c o m e f l a w e d , t r a c k 76 i s n o t u s e d .
F i g u r e 1 - 5 .
F o r d e t a i l e d i n f o r m a t i o n o n t h e I B M 3 7 4 0 d a t a f o r m a t a n d i n i t i a l i z a t i o n
r e f e r t o I B M P u b l i c a t i o n G A 2 1 - 9 1 9 0 .
J— L
OPTICAL INDEX
POST
INDEX
BYTES
73
BYTES
HEX V AL UE
ID
GAP FF
FI ELD
OR 00
13
1 1
BYTES
BYTES
HEX V A L U E
D A T A F I E L D FO RM AT
BYTES
HEX V A L U E
T r a c k s 01 t h r o u g h 7 3 , 7 5 , a n d 76 a r e a l l o c a t e d 26 s e c t o r s ,
A d a t a s e t m a y b e o n e o r m o r e s e c t o r s , i n c l u d i n g
I n t h e d r i v e , o n l y t r a c k s 01 t h r o u g h 73 a r e
SECTOR 1
188
POST IND EX F IE L D FO RM AT
40
FF OR 00
DA TA F IE L D
137
ID F IE L D FO RM AT
1
6
00
FE
L ID ADDRESS M A R K HEX C7 CLOCK BIT PATT ERN
1
6
00
FB
I
D A T A ADDRESS M A R K HEX C7 CLOCK BIT PATTERN
F i g u r e 1-5.
T h e I B M 3 7 4 0 f o r m a t i s s h o w n i n
166-2/3 MSEC
TR A C K FO RM A T
T R A I L I N G GAP
SECTOR 26
247 BYTES OF HEX FF OR 00
188
247 (VARIES WITH TOL)
6
1
00
IND EX ADDRESS M A R K
HEX FC DA TA BIT PATTERN
HEX D7 CLOCK BIT PATTERN
1
1
1
1
2
00
00
CRC
t
L SECTOR NUMBER IN B IN A R Y
TR A C K NUMBER IN B IN A R Y
2
128
D A T A
C R C
IBM 3 740 Frc
1-7
T h e d i s k d r i v e is
J — L
!
26
FF OR 00
j
GAP FF
OR 00
27
CYCLIC R E DU N DA N C Y
CHECK CHARACTERS

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