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Title: SCSI-checklist

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SCSI-checklist
When troubles according the SCSI subsystem are encountered, check out
the following list, which has proven to be very useful over time.
- Even if the SCSI bus works in DOS mode, when running Linux the
SCSI bus system has to be SCSI 2 compliant.
- Check wether the cableīs red marked wire is connected to pin
1, are the connectors plugged in tight ?
- Maybe somewhere a pin is deformed or has broken. Also the
cable should not be twisted several times, it should be kept as
straight and flat as possible. Test all self-made connections
and cables, use a new cable when you are not sure. The
distance between the SCSI Adapter and the first SCSI device
must not exceed 40 cm, between all further SCSI devices it may
not exceed 30 cm.
- Have both ends of the SCSI bus been terminated correctly ?
According to the SCSI 2 standard the SCSI bus must
have passive termination at the physical ends, it
should even have active termination at one end. If the host
adapter is located at the end of the bus, it should provide
the termination power for active termination, else another
SCSI device can supply the power. In case of all devices are
SCSI 2 standard compliant, even several
devices may provide termination power.
- When using SCSI-1, only one
device may supply termination power! Adaptec cards configure
this using the BIOS, NCRs set this directly on the card.
- When using a NCR host adapter you should enable parity check
and disable XOR for all devices. For the Adaptec host adapter
disable in the BIOS Sync Negotiation and allow
disconnected for CDROM drives, slow hard drives and SCSI
tapes.
Note according to Adaptec: disabling allow disconnected
is the save configuration, especially for
slow drives. Try this setup first and enable this feature
later (allow disconnected).
- The SCSI host adapter card might be plugged into the wrong
slot. Usually the first PCI slot (opposite the ISA slots) is
set to INTA. If the host adpater card is plugged in there,
then the BIOS PCI setup should be configured to use an
interrupt the PCI bus is able to handle. In order to do this,
consult the mainboardīs manual, as each manufacturer uses
different values. Problems may occur if the relation Slot to
INT is set up automatically: Please check the assignment and
correct the interrupts for INT manually.
- A NCR card can be set to first or second
controller (jumper). Usually (check it) the card in slot INTA
has to be set to second.
- In case of a slot is set to INTD (usually none of the 3 PCI
slots has this configuration), the card usually needs to be
jumpered to first (try it).
- The BIOS of NCR cards has to be at least Rel. 3.06.00:
NCR SDMS (TM) V3.0 PCI SCSI BIOS, PCI Rev. 2.0,
NCRPCI-3.06.0
- A multiple appearance of the 32-Bit-PCI-BIOS within the
mainboard-BIOS (kernel warning) usually means, that the board
is likely to work incorrect. Linux is not to
blame for this, but the mainboard BIOS is.
- The reason for problems with high transfer rates and drivers
might be due to an incoherent second level cache. This can be
checked by disabling the secod level cache, but enable
simultaneoulsy all PCI features (e.g.: ASUS PCI/I-486 SP3,
donīt mix up with ASUS PVI/I-486 SP3).
- For ASUS PCI/I-486 SP3G disable the GAT
option and set DRAM-Refresh to
normal.
- If nointerrupt has been assigned to the SCSI
host adapter card, it will run in polling mode (IRQ 0) when in
DOS mode. But Linux uses the interrupt mode, so the IRQ 0 is
used by the timer and the driver doesnīt work (0 hosts). This
can be found out in the directory
/proc/
in interrupts
,
ioports
and pci
(the files should be
viewed with cat
or more
, but not
with less
).

Keywords: SCSI, ADAPTEC, 2940, NCR

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SDB-kfr_15, Copyright SuSE GmbH, Nuremberg, Germany
SuSE GmbH - Last generated: 07. Oct 1999 16:53:04
by maddin
with sdb_gen 1.00.0