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FAQs for KnowledgeTek's 3-day Disk Drive Technology Class
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Maxentropic Rate for RLL Codes
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For run-length limited (RLL) codes, this is the capacity or maximum code rate that is achievable for a given set of (d,k) constraints. Remember, d is the minimum number of 0s between 1s; k is the maximum number of 0s between 1s.
To calculate the maxentropic rate, the RLL encoding rules are first represented as a state diagram. This diagram is next represented as an adjacency matrix. The maxentropic rate is the log base 2 of the maximum eigenvalue of the adjacency matrix.
Here is a table of various maxentropic rates (note, no maximum number of 1s constraints or interleave constraints are considered)
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k
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d=0
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d=1
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1
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0.6942
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2
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0.8791
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0.4057
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3
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0.9468
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0.5515
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4
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0.9752
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0.6174
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5
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0.9881
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0.6509
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6
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0.9942
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0.6690
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7
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0.9971
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0.6793
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8
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0.9986
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0.6853
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9
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0.9993
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0.6888
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10
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0.9996
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0.6909
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infinity
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1.0000
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0.6942
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Breather and Recirculation Filters
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The size of the particles that these filters pass is usually less than about 0.1 to 0.3 microns. More information is available from Donaldson Disk Drive Filtration, W.L. Gore and Associates and 3M.
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Maxtor offers a fairly comprehensive HDD glossary.
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 The whole disk drive: There are a few books that attempt to cover all of disk drive technology. The most comprehensive of these usually are written by a collection of experts from the various fields of disk drive technology. Our industry moves so quickly that these books are often outdated shortly after they are printed. For starters, leaf through the Magnetic Storage Handbook, 2nd edition, edited by C.Denis Mee and Eric D. Daniel, Published in 1996 by McGraw-Hill, ISBN 0-07-041275-8.
The PC: For a good overview of the insides of the PC -- hardware and software -- check out Peter Norton's book Inside the PC, 7th edition, Published by Sams Publishing, 1997, ISBN 0-672-31041-4.
Magnetics: For a solid, understandable overview of basic magnetic recording, check out John Mallinson's book The Foundations of Magnetic Recording. The first edition (ISBN 0-12-466625-6) was published by Academic Press in 1987, but the second edition came out a few years ago.
If you want a more rigorous and mathematically intensive look at the magnetics of writing and reading, turn to H. Neal Bertram's Theory of Magnetic Recording, Published by Cambridge University Press in 1994, ISBN 0-521-44512-4.
Heads: John Mallinson has also written a very nice book on (G)MR heads for engineers, Magneto-Resistive Heads: Fundamentals and Applications, Published by Academic Press in 1996, ISBN 0-12-466630-2.
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Please let us know if you have a question or comment.
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50th Anniversary of the Hard Disk Drive: Keynote Speech
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Place screen shot of PRMLpro here, but don't have it say "for Infiniium"
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