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Path: utzoo!utgpu!water!watmath!clyde!rutgers!ll-xn!adelie!mirror!beldar!root
From: root@beldar.UUCP
Newsgroups: comp.sys.amiga
Subject: VD0: is diseased - a MIDI killer
Message-ID: <30000006@beldar>
Date: Fri, 15-May-87 10:07:00 EDT
Article-I.D.: beldar.30000006
Posted: Fri May 15 10:07:00 1987
Date-Received: Sat, 16-May-87 17:24:38 EDT
Lines: 37
Nf-ID: #N:beldar:30000006:000:1523
Nf-From: beldar.UUCP!root    May 15 10:07:00 1987


[]

I wish it weren't true, but:

	The VD0: driver (asdg-rrd) Disable()s interupts for periods
	of time >= 600 microseconds!!! When it is IDLE, no less!
	
Why is this obnoxious?  Try servicing 31.25KB serial interupts 
at ~300 mikes each (i.e. MIDI rates) under these circumstances;
it can't be done!  VD0: is a MIDI killer... aaarrrggggh!

And now the story. I recently bought a MicroBiotics Starboard II
with a meg in it, and was delighted.  Also I installed the ASDG RRD from
Fred Fish 58, and was even more delighted until my MIDI software
failed to work.  Since I wrote it, it was easy to discover that
the problem was due to data overruns on input.  That's funny,
it's been running fine for months now, how come it died?

Well, could it be the StarBoard?  Go back to 1.1, don't addmem,
everything is peachy.  Do the addmem, all is still copacetic.
Hmmm.  Try 1.2, sans RRD.  That works.  Now I smell a rat.
Install VD0: - instant death.  Ergo... VD0: is diseased.
Notice that nothing else was running during any of these tests;
VD0: sucks up time at priority 7 even when it is idle!

Lest you doubt my veracity, the interupt routine I wrote for MIDI input
is only ~25 instructions long (VERY tight assembler), never Disable()s,
checks for additional input that showed up during servicing, and has
worked fine for quite a while now.

Anyone care to mail me a copy of someone else's PD recoverable ram disk?
Or supply some penicillin to cure my VD: ?

----	Chris Anderson
	Xyvision, Inc.
	UUCP: ...!mirror!beldar!chris