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Path: utzoo!watmath!clyde!rutgers!seismo!rochester!ritcv!cci632!djh
From: djh@cci632.UUCP
Newsgroups: comp.bugs.4bsd
Subject: Re: TC11/Cypher Tape Drive Problem (Software? Hardware?)
Message-ID: <908@cci632.UUCP>
Date: Mon, 2-Feb-87 14:06:26 EST
Article-I.D.: cci632.908
Posted: Mon Feb  2 14:06:26 1987
Date-Received: Tue, 3-Feb-87 20:21:01 EST
References: <31585@gt-cmmsr.GATECH.EDU>
Organization: CCI, Communications Systems Division, Rochester, NY
Lines: 26
Summary: Bug in 4.3bsd uda50 driver.

In article <31585@gt-cmmsr.GATECH.EDU>, rr@gt-cmmsr.UUCP writes:
> 
> I am having trouble with my Cypher 920 tape drive and Emulex TC11 controller
> under 4.3 BSD Unix (the problem did not show itself until I brought up 4.3)
> on a VAX 11/780.  The problem shows itself by giving a Bus Grant Late <BGL>
> error whenever I do a tape dump or tar at 1600 bpi.  Whenever I use 800 bpi,
> everything works fine.  DEC replaced the PE card (but not the controller card)
> with the same BGL error.

We also ran into the same problem here. As it turns out, the 4.3bsd uda50
driver increases the DMA Burst size from the default of 0 to 3. This causes
it to hog the bus for extended periods, during which the TC-11 stretches out
the Iter-Record Gap. To fix the problem change the line the reads:

	#define UDABURST 4

to read:

	#define UDABURST 2

I'm writing up a formal bug report to send to Berkeley.

Dan Hazekamp
Computer Consoles Inc.
Rochester , NY
seismo!rochester!cci632!djh