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From: krn1@ra.msstate.edu (Ken Newton)
Newsgroups: comp.sys.mac.programmer
Subject: async write to disk (MPW C)
Message-ID: <1016@ra.MsState.Edu>
Date: 28 Jan 91 16:55:30 GMT
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Organization: Mississippi State University
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I am working on a real-time application to run on a Mac fx that 
requires very fast data collection to disk.  The program is in MPW C
and I use the following calls to try to speed up the write and to 
allow the data collection to proceed while the disk is writing.
     ioerr = PBAllocContig( myPB, false);  /* allocates enough contig space */

in loop:
     collect a block of data (13K bytes)
     wait for ioResult == 0 from last write  
     PBWrite(myPB, true);     /* async true -- DOES NOT SEEM to work */
end loop

The write is taking about 50 msec and returning with ioResult already 0.  I.e.
the call does not get done in async fashion.  For this to work for our 
application, the call needs to return in less than 1 msec and (probably) has
to use the DMA capabilities of the fx.

Any suggestions?  This is my first venture in to MPW C programming after many
years with Pascal on Lisa and Mac.

Ken Newton
Mississippi State University
krn1@ra.msstate.edu
krn1@msstate.bitnet
krn1@vax.dial.msstate.edu