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From: dyer@harvard.UUCP (Steve Dyer)
Newsgroups: net.unix-wizards
Subject: Re: weirdness with DMF-32 sync, Qniverter, and uVAX-II...
Message-ID: <923@harvard.UUCP>
Date: Mon, 5-May-86 11:07:11 EDT
Article-I.D.: harvard.923
Posted: Mon May  5 11:07:11 1986
Date-Received: Wed, 7-May-86 01:48:02 EDT
References: <281@spdcc.UUCP>
Organization: Aiken Comp Lab, Harvard
Lines: 31
Keywords: adb -w /dev/kUmem; the twilight zone
Summary: all fixed

In article <281@spdcc.UUCP>, dyer@spdcc.UUCP (Steve Dyer) writes:
> 3.) The DMF sync driver has a number of busy loops in the open and close
>     routines which have always managed to break out within milli- or micro-
>     seconds on the 750.  However, these bad coding practices have turned
>     into monsters on the MicroVAX!  Briefly, the code fragments look something
>     like this:
> 	dmfsaddr->dmfsmr = DMF_MR;	/* 0x80 master reset */
> 	while(dmfsaddr->dmfsmr & DMF_MR) DELAY(10);
>     The "master reset" bit is held high until the DMF sync line has finished
>     resetting.  On the uVAX, the bit is never reset.
> 	% adm -w /dev/kUmem
> 	0x08xxxxx?w 0x80 (where 0x08xxxxx is the mapped "UNIBUS" address
> 			  of the DMF sync misc register above)
>     resets the device address, so that 0x80 is no longer held high.
> 

Just in case anyone was losing sleep over this, and to clear the name of
Able, the maker of the Qniverter II, I should mention that the problem
ultimately was hardware--Unibus DMA boards placed in slots with NPR jumpers,
and other non-DMA boards in those with the NPR jumpers removed.  (Hey, I'm
just the software person.)  The Qniverter seems to have an isolating effect;
placed after all the Qbus devices, it allowed for weird behavior as above,
something you'd probably never see on a true UNIBUS machine.  Placed before
them, the Qbus, naturally, gets hung.

As of right now, the Qniverter II is working fine with our UNIBUS peripherals
on the mVAX-II.
-- 
/Steve Dyer
dyer@harvard.harvard.edu
harvard!dyer