Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucsdhub!hp-sdd!hplabs!hpl-opus!hpccc!hpcc01!hpwrce!ted
From: ted@hpwrce.HP.COM ( Ted Johnson)
Newsgroups: comp.sys.mac.programmer
Subject: double buffering considered harmful?
Message-ID: <7430027@hpwrce.HP.COM>
Date: 18 Jan 90 20:16:33 GMT
Organization: Ye Olde Salt Mines
Lines: 23

I just noticed that my SE (running 6.1/6.0.3) doesn't do double
buffering when copying files from a floppy to the internal
hard disk.  Is there some technical reason why the Finder
doesn't do this?  Seems like this would
be a cheap way to get a performance increase....


DESIRED SCENARIO:
1)read from floppy (hard disk remains idle)
2)write to hard disk (floppy drive remains idle)
3)if not done, goto 1

DESIRED SCENARIO:
1)do an asynchronous read from floppy to memory buffer A;
  In the meantime, the previous read from floppy, which was stored in
  memory buffer B, gets written to the hard disk. 
2)when the async. read from floppy completes, it interrupts and 
  then the hard disk reads  from buffer A to the hard disk.  Meanwhile
  the floppy drive starts a new async. read, moving the bytes read to
  buffer B.
3)if not done, goto 1

-Ted