Thread View: net.micro.atari16
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Started by braner
Sun, 02 Nov 1986 20:15
Patches for the RAM disk program
Author: braner
Date: Sun, 02 Nov 1986 20:15
Date: Sun, 02 Nov 1986 20:15
50 lines
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2714 bytes
[]
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
Re: Patches for the RAM disk program
Author: rbk
Date: Tue, 04 Nov 1986 12:56
Date: Tue, 04 Nov 1986 12:56
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1936 bytes
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<><><><><><><><>
> 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:
> ... (some lines deleted) ...
> 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
The patch works as advertised; thanks Moshe!
BTW, I changed the byte to "0C" for Drive "M" since
I already have a hard disk partition called "F".
R. Brad Kummer {ihnp4, seismo!akgua}!akguc!rbk
AT&T Bell Labs Atlanta, GA
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