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Major Features Of Dds Drives; Dds-Dc Drive - HP Model 705 - Workstation User Manual

Hp dds-2 tape drive user's guide (a1658-90701)
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Major Features of DDS Drives

The DDS-1 format incorporates error correction techniques used in audio DAT drives
with additional techniques specifically designed to provide the integrity of data necessary
for computer use. These extra methods of error detection and correction are as follows:
C3 ECC, a third level of Error Correction Code providing correction across frames
within groups.
Read-After-Write, where data is verified immediately after it is written and re-
written if there is any error.
Data Randomizer, for recording the data in order to provide a consistent signal
level. This enables read-after-write to be effective.
Track Checksums, for detecting and locating helical errors, and so improving the
performance of C3 ECC.

DDS-DC Drive

The HP Model C1536A implements the DDS-DC format. This includes all of the features
of the DDS-1 format, plus an extension to include data compression as follows:
Compressed data can be stored in a way that maintains the full functionality of
the DDS format and ensures backwards compatibility with existing DDS drives.
Any DDS-1 and DDS-DC cartridge can be read, whether data compression is
switched on or off.
Data is automatically decompressed on reading even if data compression is switched
Mixing compressed and uncompressed data is supported. This means that a car-
tridge can be written with uncompressed data and read in any DDS drive.


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