[vcf-midatlantic] vax scsi questions

VAXman at tmesis.org VAXman at tmesis.org
Sun Oct 8 13:52:34 EDT 2017

Jim Scheef via vcf-midatlantic writes: 

>Bill, Are the two SCSI port two separate bus or two ports on the same
>bus (controller)? If there is only one bus, terminate the empty
>connector. If there are two bus, turn off the empty bus. This is
>standard SCSI. Duplicate SCSI ID's are a no-no and must be fixed. All
>devices on the bus must has a unique ID. Hope this is what you asked.

Which MicroVAX 3100 model?  

In general, each device on a SCSI bus must have a unique SCSI address.
If, for example, two drives are address as SCSI id 3, you'll find you
will have issues with both or corrupt one or both drives.  Typically,
the MicroVAX startup firmware will probe the SCSI bus and complain if
there are SCSI id conflicts.

Some MicroVAXes in the 3100 series came with two SCSI busses.  There
are designated A and B.  The SCSI id for the MicroVAX controller was
typically 7; so devices could be attached with ids from 0 to 6.  The
naming of the devices, when VMS is booted are:

ddcn:  when dd is the name of the driver controlling the device.  If
the device is  disk, this is DK (DKDRIVER).  If the device is a tape,
it's MK (MKDRIVER).  The 'c' in the device designation if the adapter
upon which the device is located.  If there are two adapters, this is
either A or B.  The 'n' is the device number.  Unless you're looking
as a dvices served from a storage controller, the sub-LUN vallues are
0.  So on your MicroVAX, you see somehting like a DKA300: for a disk
addressed as SCSI id 3 on the A adapter.

If you need more info, ask.

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