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From: jcd@pitt.UUCP (Jim Durham)
Newsgroups: comp.sys.dec
Subject: MV II Hardware help
Keywords: TK 50, RD 53
Message-ID: <8791@pitt.UUCP>
Date: 4 Oct 90 17:25:31 GMT
Organization: Computer Science Dept., Univ. of Pittsburgh
Lines: 27


Would anyone care to hazard a guess as to this fault in a TK-50
controller card? : It works as long as the DECQNA is not
'ifconfigged'. Substitution of cards reveals that the fault is
indeed on the TK-50 controller and not the DECQNA. Changing
chips that have leads going to interrupt and dma control bus
lines didn't fix it. Oh yes.... card position on the bus has
no effect on the problem. The TK50 still fails when the Ethernet
controller is fired up.

Second question: Does anyone know exactly what goes on with
an RQDX2 controller and non-DEC drives. I have received several
answers. One is that DEC writes a "descriptor block" out to the
drive to tell the controller what kind of drive it is. Without
this, according to this scenario, the formatter won't format
the drive. The other answer is that I need to change the
mysterious 'R7'. What is 'R7' ? A jumper? A resistor. I need
to know what it actually *does*, because, since I'm interested
in using a non-DEC drive, it won't have 'R7' and I'll have to
fudge a substitute. Does this have anything to do with tying
write protect high thru a 1k resistor?

Any answers or guesses greatly appreciated !

Thanks,

Jim Durham