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Path: utzoo!watmath!clyde!rutgers!cbmvax!carolyn
From: carolyn@cbmvax.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: Help! I can't seem to run a program > 2meg in my 4meg Amiga
Message-ID: <1329@cbmvax.cbmvax.cbm.UUCP>
Date: Mon, 2-Feb-87 17:04:10 EST
Article-I.D.: cbmvax.1329
Posted: Mon Feb  2 17:04:10 1987
Date-Received: Tue, 3-Feb-87 18:39:41 EST
References: <12032@lanl.ARPA>
Reply-To: carolyn@cbmvax.UUCP (Carolyn Scheppner)
Organization: Commodore Technology, West Chester, PA
Lines: 110

In article <12032@lanl.ARPA> jtw@lanl.ARPA (James West) writes:
>Could someone please explain why an AMIGA with a 4 megabyte memory expansion
>will only run tasks that total to 2 megabytes or less???
>
>Recently I added an AMERISTAR expansion bus with two 2 megabyte memory boards
>and a hard disk.  I am running the new Amiga 1.2 operating system with the
>Absoft Fortran compiler.  AmigaDos 1.2 auto configures memory, and
>automatically sees the 4 megabytes.  I can easily copy 4 megabytes of files
>into the memory without any problems.  It appears part of the operating system
>sees the 4 megabytes, but part does not.  To be exact, the part of the
>operating system dictating memory available for running processes, appears
>to be seeing only 2 megabytes!
>...

   Separate memory boards (such as Jim's 2 2-meg boards) are configured
as separate entities, each with its own entry in the system MemList
and its own MemHeader in its first 32 bytes.

   Jim's programs apparently need a contiguous chunk of memory larger
than what is available in either individual board.  The following
program "MergeMem.c" attempts to merge the MemList entries of
sequentially configured ram boards.  I tested it with a 1/2 meg Alegra
plugged into the pass-thru of a 2-meg StarBoard.  It successfully
merged the MemList entries of these two boards.  After the merge,
I was able to AllocMem() a 2.1 megabyte chunk.

------------------------------------------------------------------------

/* MergeMem.c - by  Carolyn Scheppner  CBM  02/87
 *  Attempts to merge the memlists of sequentially configged ram boards
 *  which have the same Attributes (for contiguous expansion ram)
 *
 *  Note:  This program has been tested with an Alegra plugged into
 *         a Microbotics Starboard' pass-thru.  The program makes
 *         the assumption that sequentially configged ram boards
 *         have sequential entries in the MemHeader list.  If this
 *         is not always true, then this program may not work for
 *         some expansion configurations.  Works fine for me though.
 */

#include "exec/types.h"
#include "exec/exec.h" 
#include "exec/execbase.h" 

extern struct ExecBase *SysBase;

main()
   {
   struct MemChunk *chunk;
   struct MemHeader *mem, *firstmem, *prevmem = 0;
   struct ExecBase *eb = SysBase;
   ULONG  memsize;

   /* Temps */
   struct MemChunk *oldFirst;
   APTR   oldLower, oldUpper;
   ULONG  oldFree;

   Forbid();
   firstmem = (struct MemHeader *)eb->MemList.lh_Head;

   /* Go to end of MemHeader list */
   for (mem = firstmem;
           mem->mh_Node.ln_Succ;
              mem = (struct MemHeader *)mem->mh_Node.ln_Succ)
      printf("Found memory type $%lx at $%lx\n",mem->mh_Attributes,mem);

   /* Back up from terminal node to point at last MemHeader */
   mem = (struct MemHeader *)mem->mh_Node.ln_Pred;

   /* Backwards, for each except first */
   for ( ; (ULONG)mem != (ULONG)firstmem; mem = prevmem)
      {
      prevmem = (struct MemHeader *)mem->mh_Node.ln_Pred;

      /* If prev MemHeader describes neighboring ram of same Attributes */
      if(((ULONG)prevmem->mh_Upper == (ULONG)mem->mh_Lower - 32)&&
           (prevmem->mh_Attributes == mem->mh_Attributes))
         {
         printf("Merging $%lx with $%lx\n",prevmem,mem);
         /* Save needed stuff from MemHeader before Remove()ing it */
         oldFirst = mem->mh_First;
         oldLower = mem->mh_Lower;
         oldUpper = mem->mh_Upper;
         oldFree  = mem->mh_Free;
         Remove(mem);

         /* Adjust Upper and Free in prev MemHeader to include this mem */
         memsize = (ULONG)oldUpper - (ULONG)oldLower +32L;
         prevmem->mh_Upper = (APTR)((ULONG)prevmem->mh_Upper + memsize);
         prevmem->mh_Free += oldFree;

         /* Link last free chunk of prevmem to first free of mem */
         for (chunk = prevmem->mh_First;
                  chunk->mc_Next; chunk = chunk->mc_Next);
         chunk->mc_Next = oldFirst;

         /* Now FreeMem() the old MemHeader as a 32 byte chunk */
         FreeMem(mem,32);
         }
      }
   Permit();
   }

-- 
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Carolyn Scheppner -- CBM   >>Amiga Technical Support<<
                     UUCP  ...{allegra,caip,ihnp4,seismo}!cbmvax!carolyn 
                     PHONE 215-431-9180
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