Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rochester!cornell!batcomputer!braner
From: braner@batcomputer.TN.CORNELL.EDU (braner)
Newsgroups: net.micro.atari16
Subject: Patches for the RAM disk program
Message-ID: <1354@batcomputer.TN.CORNELL.EDU>
Date: Sun, 2-Nov-86 15:15:44 EST
Article-I.D.: batcompu.1354
Posted: Sun Nov  2 15:15:44 1986
Date-Received: Tue, 4-Nov-86 00:27:39 EST
Reply-To: braner@batcomputer.UUCP (braner)
Organization: Theory Center, Cornell University, Ithaca NY
Lines: 50
Summary: Can be used as drive 'C' or 'F'

[]

If you want to use the RAM disk program I've posted as a drive other
than 'D', you have to patch it.  This patch is essential if you want to use
a hard disk together with the RAM disk.  Here is an old hint:

>From: jdg@elmgate.UUCP (Jeff Gortatowsky)
>	{allegra,seismo}!rochester!kodak!elmgate!jdg
>Subject: Reset survivable RAM disk and Atari HD problem fixed!
>Date: 3 Oct 86
>
>Well after a bit of digging and disassembly my brother (a sharp troop)
>found the correct combination to get the reset surviving RAM disk to play
>as drive F: in a HD system (Atari 20meg).   First, as was mentioned
>before on this news group you need to change the bit set in the 'drivebits'
>variable down in low memory.  The BSET #3,d0 needs to be BSET #5,d0 (for
>drive F:).  The other patch is applied to the compare instruction in the
>code that is executed when RWABS calls the RAM Disk.   The RAM disk checks
>the device number and if it's not the right number it passes control
>through a JMP instruction to the Hard disk vector the RAM disk saved at
>boot time.  The above patches imply that the RAM disk need be executed
>AFTER the hard disk driver is installed, so it may take over and save
>the hard disk vectors.

What I think was meant:  Change the bytes at the following
offsets from the beginning of the ".prg" file:

	  offset	old value(for drive D)	new value (for drive F)
	  ======	======================	=======================

	$145 (325)		03			05
	$173 (371)		03			05
	$181 (385)		03			05
	$193 (403)		03			05

The first one is the "BSET #3,D0" in the installation, the other three
are "CMP #3,x(A7)"s in handling calls to disk device drivers.

For drive C instead of F, use the value 02.

To change the default RAM disk size, change the byte at offset
$B3 (179): The value is the size in units of 64K, e.g. 03 for
a default size of 192K, 09 for 576K.

WARNING:  These are untested speculations!!!
If somebody tests this (with a hard disk, if possible), please tell us!
Jeff, if you're out there: please confirm &/or post the fix and the
disassembly!

- Moshe Braner