TC11/Cypher Tape Drive Problem (Software? Hardware?)

[djh at cci632.UUCP]

In article <31585 at gt-cmmsr.GATECH.EDU>, rr at 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