Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!wasatch!ug.utah.edu!u-mderha
From: u-mderha%ug.utah.edu@wasatch.UUCP (Max Derhak)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Got those 48K blues...
Summary: Upgrades can be messy
Keywords: memory, upgrade, 8bit
Message-ID: <1401@wasatch.UUCP>
Date: 22 Mar 89 23:20:29 GMT
References: <6289@medusa.cs.purdue.edu>
Sender: news@wasatch.UUCP
Reply-To: u-mderha%ug.utah.edu.UUCP@wasatch.UUCP (Max Derhak)
Organization: University of Utah, Computer Science Dept.
Lines: 52

In article <6289@medusa.cs.purdue.edu> smb@cs.purdue.edu (Scott M Ballew) writes:
>
>I have an Atari 800 (the old kind) and although I want to get a bigger, newer
>machine, I am confined by my budget to wait on that.  In the interim, I want
>to try to expand the memory of this machine beyond the current 48k.

> (other Stuff goes here.)

>Thanks,
>Scott Ballew
>Bitnet: privateer@drycas.bitnet
>Internet/UUCP: smb@cs.purdue.edu

Upgrades to the old atari 8-bits are rather messy.  A friend of mine
(Ron Bolling of UPGRADE Productions) does upgrades for just about every
one of the 8bit line.  I have an 800 with 320k, but it is addressed
differently than any other upgrade i know of.  There are many ways of
addressing ram in 8bit atari's.  Exactly how do you want it to be addressed?
If you want compatability with the XL/XE computers, then you need to be able
to address memory underneath the operating system via the pia address.
Mosaic memory systems used to produce an upgrade that did that.  In addition
to being able to address all of your memory as RAM (64k), there are various
ways of exceeding this by using memory banking.  The 130XE (and compatables)
use 16k banks in memory from $4000 to $7FFF.  The bank selection is also
done through pia port B.  The Axalon system banks in the same place, but
is banked through a register located at $CFFF.  The Mosaic Ramdisk banks
only in 4k banks in memory locations $C000 - $CFFF, and is selected by 
writing to memory locations $FFC0 -$FFE0.
My 800's system is completely different.  We affectionately call it the
64k+.  The operating system memory as well as memory (cartridge) protection
is enabled by a write only register somewhere in the unused I/O addresses.
The extra (RAMDISK) memory is banked in two locations. First in 4k Blocks
from $C000 to $CFFF, and then in 256 byte blocks from $D700 to $D7FF.
The upgrade provides for deselection as well as memory protection (simulated
ROM) for these memory locations.  They are also banked via write only regs
in unused I/O memory locations ($D000-$D7FF). Ron also has a simular upgrade
for atari 400's, but there are a few things left out due to the archatecture
of the 400.
Ron has also come up with a complete memory system for XE's which gives
cartidge memory protection, operating system ramdisk support, and expanded
memory up to 2 meg.  This is made possible by the addition of an extra PIA.
I have one of these, and let me say that its great!

I don't know much about getting the axalon/mosaic upgrades, but Ron still
does them.  (A couple of months ago, he upgraded a 16k 400 to 52k for a
friend of mine.)  I don't know about his current pricing though.  If your
intrested in finding out about any upgrade Ron does, just send me e-mail,
and I'll try and find out.

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   (Take it to the) Max Derhak : u-mderha@ug.utah.edu.UUCP
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