Maxtor D740X-6L 20.0 AT Product Manual page 62

B a s i c P r i n c i p l e s o f O p e r a t i o n
       5 M G Y 1 H H U G V U
C y l i n d e r S k e w
0 Q V G
       4 W P V K O G % C N E W N C V K Q P
Since the wedge-to-wedge time is constant over the entire disk, a single set of head
and cylinder skew offsets will fulfill the requirement for all recording zones. The
formula used to compute the wedge skew for a given cylinder and head is:
Wedge skew=[C* ((# of heads – 1) * TS + CS) + H * TS] MOD 196
Where:C=Cylinder number
H=Head number
TS=Head Skew Offset
CS Cylinder Skew Offset
(wedges/track=196)
     ' T T Q T & G V G E V K Q P C P F % Q T T G E V K Q P
As disk drive areal densities increase, obtaining extremely low error rates requires a
new generation of sophisticated error correction codes. Maxtor D740X-6L hard disk
drive series implement 320-bit Reed-Solomon error correction techniques to reduce
the uncorrectable read block error rate to less than one bit in 1 x 10
When errors occur, an automatic retry of 15 10-bit symbols and a more rigorous 16
10-bit symbols correction algorithm enable the correction of any sector with single
bursts, or up to sixteen multiple random one 10-bit symbol burst. In addition to these
advanced error correction capabilities, the drive uses an additional cross-checking
code and algorithm to double check the main ECC correction. This greatly reduces
the probability of a miscorrection.
       $ C E M I T Q W P F + P H Q T O C V K Q P Q P ' T T Q T % Q T T G E V K Q P % Q F G C P F ' % % 1 P V J G ( N [
A sector on the Maxtor D740X-6L drive is comprised of 512 bytes of user data,
followed by four cross-checking (XC) bytes (32 bits), followed by 40 ECC check
bytes (320 bits) or 32 10-bit symbols. The four cross-checking bytes are used to double
check the main ECC correction and reduce the probability of miscorrection. Errors
5 - 1 3 M a x t o r D 7 4 0 X - 6 L 2 0 . 0 / 4 0 . 0 / 6 0 . 0 / 8 0 . 0 G B A T
6 C D N G  
H e a d S k e w
Nominal wedge-to-wedge time of 42.5µs is used. Worst case in-
stantaneous spindle variation (±0.12%) is used while calculating
to provide a safety margin.
Wedge offsets are rounded to the closest whole number.
S k e w O f f s e t s
5 9 + 6 % * 6 + / '
1 . 8 3 m s
T B D m s
9 ' & ) ' 1 ( ( 5 ' 6
4 3
4 3
bits read.
1 4