From: Gerhard Hertlein (
Date: Mon Oct 17 1994 - 07:47:41 CDT


some days ago I asked two questions about the DAT drive HP C1533A:

1. DIP-switches on the device
2. density bytes in /sys/sundev/streg.h (SunOS 4.1.2)

Many thanks to:

The outcome was:

1. SW 1 on = Data Compression enabled
   SW 2 on = Host Control of data compression enabled
   SW 3 on = Media Recognition System disabled
   SW 4-8: Select SCSI profile

   A best fit of the conflicting advises for switch settings for SUN is:
   SW 1 = on
   SW 2 = off (Sun cannot control data compression, see 2.)
   SW 3 = off (Media Recognition enabled)
   SW 4,5 = on
   SW 6,7,8 = off
   (SW 8 is disputed)

2. SUN cannot control compression when writing tapes, since the drive
   does not understand the density bytes in the kernel configuration
   file (set all four to zero).
   Compression mode can be controlled with the SCSI compression mode page
   which is however unsupported by SunOS (Solaris?).

   So the advice was to disable host control of data compression (SW 2 off)
   and leave compression enabled (SW 1 on)

Gerhard Hertlein
Philips Kommunikations Industrie AG
Dept. LN
D-90327 Nuremberg
Fed.Rep of Germany

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