Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: What Happens If You Have > 9 Meg??
Message-ID: <17711@cbmvax.commodore.com>
Date: 17 Jan 91 15:00:36 GMT
References: <6931@crash.cts.com> <744@cbmger.UUCP> <677@caslon.cs.arizona.edu>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 39

In article <677@caslon.cs.arizona.edu> dave@cs.arizona.edu (Dave P. Schaumann) writes:
>In article <744@cbmger.UUCP>, peterk@cbmger.UUCP (Peter Kittel GERMANY) writes:
>|In article <6931@crash.cts.com|lgreen@pnet01.cts.com (Lawrence Greenwald) writes:
>||I've always been curious about the 9 Meg limit on the 2000. What would happen
>||if I were to have more than 9 meg in the machine...

>|[ extra memory would not be recognised ]

>How about writing some kind of device driver that would recognise the
>additional RAM and use it as another RAM: disk?  Sort of like the memory
>expansion boxes that are around for the C64/128 line (sorry, I forgot the
>part #).

Nope, that's not going to work.  Briefly, here's how the AUTOCONFIG logic see
things.  It loops through boards, each of which in turn asserts its 
configuration register block in the 64K slot starting at $00e80000.  Each 
board indicates the memory space it requires in this configuration information,
and usually the OS decides where that board goes, and writes that configuration
address to the board.  If there isn't enough space, the board can't be added 
to the system at all.  Most boards support the "shutup" feature, which allows
the OS to make a board simply disappear, allowing it to get to any boards after
which may be small enough to still fit in the available memory space.  

The C128 memory expansion devices are specifically designed to support banked
memory (they actually have a DMA device which does fast block memory movements
faster than the C128 can do them).  You could build something like this for 
the Amiga, of course, but you can't talk a generic memory board and make it
bank switch like this.

>|Best regards, Dr. Peter Kittel  // E-Mail to  \\  Only my personal opinions... 

>Dave Schaumann		|  And then -- what then?  Then, future...


-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
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