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From: entropy@rice-chex.ai.mit.edu (enthalpy)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: 1.44M 3.5 disks  //  floppies as swap space
Message-ID: <10562@life.ai.mit.edu>
Date: 10 Sep 90 19:04:52 GMT
References: <1990Jul31.165603.20869@msuinfo.cl.msu.edu> <1407@wet.UUCP> <1990Sep10.105324.26957@agate.berkeley.edu>
Sender: news@ai.mit.edu
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In-reply-to: kawakami@monsoon.Berkeley.EDU's message of 10 Sep 90 10:53:24 GMT

In article <1990Sep10.105324.26957@agate.berkeley.edu> kawakami@monsoon.Berkeley.EDU (John Kawakami) writes:

   In article <1407@wet.UUCP> nut@wet.UUCP (adam tilghman) writes:
   >In article <1990Jul31.165603.20869@msuinfo.cl.msu.edu> schultzd@kira.uucp (David Schultz) writes:
   >>
   >>2.)  Is there any program that allows you to use a floppy drive as
   >>swap space to get more memory in an ST.  I realize this would be
   >>painfully slow, but until I can afford more mem, it would have to do.
   >>It would be infinitely more helpful on a nig hard drive.  (Set aside
   >>an x meg partition on the hard drive and treat it as internal memory.
   >>Virtual mem on the ST!!!)
   >
   >  If you are using just a plain-vanilla 68000 in your machine, this is
   >completely impossible.  If you have installed a 68010 in your ST (I tried

   Well, not practical, not nice, not useful, but definitely possible.  You
   (the intrepid programmer) write a new malloc which returns pointers to
   pointers: aka handles.  The pointer returned is a pointer into a table;
   the table is made up of pointers to memory fragments.  Toss in some
   swapping algorithms and you have a private VM system which can defrag
   memory and do other neat stuff.  If you are the of the TOS-sux-so-I'll-
   install-my-own-OS types, this would not be unfathomable.


No!  You would still have to handle the case where someone actually
tries to _access_ data that has been paged out (you mean you have to
be able to read it back??).  This entails first of all being able to
recognize an interrupt caused by accessing memory that was paged out
(this part might be possible) but after paging that data back in, you
have to be able to continue from the interrupt as if nothing had ever
happened.  The fact that this is not a supported operation on the
68000 makes it unlikely that such a program could be written.

nick
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