[Info-vax] SCSI question (KZPEA-CX adaptor)

[Richard B. Gilbert]

Christoph Gartmann wrote:
> In article <001c5c77$0$19603$c3e8da3 at news.astraweb.com>, JF Mezei <jfmezei.spamnot at vaxination.ca> writes:
>> I finally installed a KZPEA-CX adaptor on a DS10L.
>>
>> I had some adaptor that fitted onto the external plug of the KZPEA-CX
>> and provided a standard 50 pin ribbon cable interface.
>>
>> Plugged in a CD drive (old Sony drive very similar to the RRD42). The
>> SRM console would see the drive, get its identity, generate a DKA400:
>> device. But couldn't boot from it.
>>
>>>>>> show dev
>>> dka400.4.0.17.0            DKA400        SONY CD-ROM CDU-8003A  1.8f
> [...]
>> So it detects that this old SCSI drive is a narrow ("no" to "Negotiate
>> Wide") and that it doesn't suport tagged queuing.
>>
>> However, trying to do a "Verify media" results in it telling me it isn't
>> a disk device.
>>
>> However, booting into VMS:
>>
>>
>>> $ show dev $10$dka400:/full
>>>
>>> Disk $10$DKA400: (BIKE), device type SONY CD-ROM CDU-8003A, is online, file-
>>>     oriented device, shareable, served to cluster via MSCP Server, error logging
>>>     is enabled.
>>>
>>>     Error count                    0    Operations completed                  0
>>>     Owner process                 ""    Owner UIC                      [SYSTEM]
>>>     Owner process ID        00000000    Dev Prot            S:RWPL,O:RWPL,G:R,W
>>>     Reference count                0    Default buffer size                 512
>>>     Allocation class              10
>> But:
>>
>> $ mount/nowrite/override=id    $10$dka400: test
>> %MOUNT-F-MEDOFL, medium is offline
>>
>>
>> I Have tried this with different setups, including plugging the 50 pin
>> ribbon cable directly into the KZPEA card's internal 50 pin connector.
>>
>>
>> QUESTIONS:
>>
>> If the controller is able to find out the identity of this device,
>> notice it isn't wide etc:
>>
>> 	-does this mean that the connection (cable, adaptor etc) is fully
>> functional?
> 
> No, this means that there is some data exchange between the CD-ROM and the
> host and hence, there must be some sort of connection.
> 
>> or are there primitive exchanges (such as getting
>> information from device) which can be done with a deffective connection
>> but when you try to do real access to the device , it fails ?
> 
> This is pretty common.
> 
>> 	-the card is set to have auto termination. Would an unterminated  CD
>> ROM drive at the other end of the cable cause this behaviour ? I'd have
>> to search for the specs of this drive to see if it is terminated or not.
> 
> Termination is important. I wouldn't rely on auto-termination. The last device
> on the bus has to be terminated. Thus, enable termination on the drive and
> disable auto-termination on the card.
> 

Remember that BOTH ends of the bus must be terminated and that each end 
must be terminated ONCE and ONLY ONCE!  Ninety plus percent of SCSI 
problems are due to missing/improper termination of the bus!