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From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: net.micro.amiga
Subject: Re: Re: Question on Asyncronous IO message ports
Message-ID: <8609150632.AA26777@cory.Berkeley.EDU>
Date: Mon, 15-Sep-86 02:32:48 EDT
Article-I.D.: cory.8609150632.AA26777
Posted: Mon Sep 15 02:32:48 1986
Date-Received: Mon, 15-Sep-86 22:07:04 EDT
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Organization: University of California at Berkeley
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>From Phillip Lindsay
>\From Neil Katin:
>
>"The user cannot have more than one packet outstanding to an individual
> handler at once.  This is especially true for things like CON:, SER:,
> etc."
>
> "For the file system, one can only have one packet per open file
> handle."

	Earlier versions of my asyncronous write addition to my XSTDIO
library crashed, and they just happened to be queuing more than one
packet on the handler's port.  Now I know why, but it would be 
interesting if someone at amiga would comment as to why this restriction
exists.

	However, it does NOT mean asyncronous I/O can't be done.  As soon
as I make sure my library adhears to these restrictions, I'll post it.

	Consider the following senerio:

	-Queue a 40K write to some file on df1:
	-While that write is taking place attempt to read from some file
	 on df0:

	I tested this sort of thing by modifying the source to 'backup'
slightly to use the new async-feature.  However, it was only a mere 3%
faster.  This is due to the fact that both handlers must ultimately
share the disk-bus for DF0: and DF1:... I think much better results
would occur if you were going between a DFx: and an HDx:, or from DFx:
to SER: (or something like that).

	I think, however, that you modem-program writers will like
the feature for your 'capture' mode... since writes happen infrequently,
making the asyncronous is a real boon because it virtually eliminates
the delay you normally see when the thing goes to disk.

	This time I'll include the documentation, but post the library
uuencoded (so you don't have to compile it all).  If you want the source
just mail me and I'll send it to you.

				-Matt