cs2532aa@unm-cvax.UUCP (03/18/85)
What follows is an excerpt from issue 9 of Hardcore COMPUTIST, a magazine that
due to its controversial subject matter (defeating software copy-protection) is
not available everywhere. This issue in which this appears is also out of
print. It describes a technique that should allow persons to use ProDOS on an
Apple compatiable.
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Using ProDOS on a Franklin Ace
The March, 1984 issue of Apple Assembly Lines contained a short article
containing instructions on how to successfully boot ProDOS on a Franklin
Ace computer. Thus method involved NOPing two bytes in the PdoDOS system
file after it had been loaded into memory. However, this method would not
work for the ProDOS file dated 01-Jan-84.
The ProDOS system file contains a checksum-like routine which returns a value
of $0C if a genuine Apple is detected and a $00 otherwise. If a non-Apple is
detected ProDOS will just hang up and not load in the BASIC.SYSTEM interpreter.
. . .
In order for this routine to always return with a value of $0C, the branch to
the code which loads the accumulator with $00 (LDA #$00) needs to be removed.
This can be done by replacing the BNE $2660 (D0 03) instruction with two NOPs
(EA EA).
The easiest way to do this is to use a sector editor and zap the change
directly to the disk. Any sector editor can be used on a ProDOS disk because
the formatting has not been changed from DOS 3.3. On my copy of the ProDOS
USERS DISK the change I had to make was to bytes $5B and $5C of Track $01,
Sector $09. I changed them from D0 03 to EA EA and rewrote the sector.
If you have a sector editor with search capability, such as ZAP [from the
disk "Bag of Tricks", by Don Worth and Pieter Lechner of "Beneath Apple DOS"
fame], you should search for a byte sequence of 69 0B D0 03, since the
sequence of D0 03 is a fairly common one.
Once you have made this change, ProDOS should boot and operate on Franklins
and other Apple compatiables that have their monitor ROM routines in the
proper locations.
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I hope this article helps. I have not had to try it, because I bought a REAL
Apple. I would suggest that the serious user do the same.
.rne.
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Real World . . Ernie Longmire / 311 Don St. SE / Los Lunas, NM 87031-9405
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