Re: cracked Apple II disks

In article <1151632511.333886.217830@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
michael.pohoreski@xxxxxxxxx says...

Tim923 wrote:
What was involved in removing the copy protection on disks so they
could be copied?

I remember trying to copy some and getting a bunch of random
characters on the screen indicating a failed copy.

It depends on how old the game is, which determines the sophistication
of the copy protection.

...game? :-) ....you reveal what kind of world you live in....

FYI: not all Apple II disks contained games. Some non-game disks were
copy protected too....

Simple games just changed the D5 AA 96 nibble prefix (and/or the suffix
too) of a sector, to some other non standard value.

Visicalc was copy protected in just that way. and if it wasn't for
Visicalc, the Apple II would probably not have become as popular as it
did.


Other tricks involved storing the track data on half-tracks, or
quarter-tracks. Some nasty ones would read a sector (or 2), advanced
the (disc) head 1/4 track, read another sector (or two), etc. I
believe Choplifter did this.

More nefarious is illegal nibbles. Technically, you're not supposed to
be able to store a nibble with 2 consecutive zeros in it, but in
practise there were a few values allowed by the disk controller.

There are a quite a few permutations of the tricks to make a disk
uncopyable. Fortunately, if it can be read, it can be copied.

The first order of business is boot-step tracing, since the the first
sector HAS to have the standard prefix (or else the disk controller
won't recognized it) which is loaded in at $800.

The second order of business, is to disable the Ctrl-Reset from
rebooting the machine. There are ways to do this. One of the easiest
was on the Apple ][+ with a 16K LC: you can copy ROM to LC RAM, change
the reset vector so it jumps to the monitor, and write protect the LC
RAM.

If you give us the name of the game, we could trouble-shoot the problem
easier, since most games have been "identified"

I'd also recommended playing with Copy ][+ since it had a lot of
parameters one could customize in getting that perfect nibble copy.

Beneath Apple Dos is a mandatory reading.

Lastly, you'll want to track down "Cracking Techniques 1983, and 1984"
to get an overview and details on how to remove some of the protection
used in the day.

There was also hardware that helped. Wildcard / Replay, was a popular
card that took a 'snapshot' of the apple memory, and then dumped it to
.

Relevant Pages

  • Re: Hardware musings
    ... By now _ALL_ apple II 5.25 floppy disk that have protection have been produced and most of them have been hacked and their general operation is understood even if not normalized and deprotected fully. ... I was never able to crack Silent service nor normalize Prince of Persia.) ...
    (comp.sys.apple2)
  • Re: working on Apple ][ emulator, need volunteers
    ... gates, but logic simulation, as sampled by clock pulses. ... of places where the Apple II design misses the ... Apple II cannot detect a particular disk state, ... Such a protected game would have to be run without write protection ...
    (comp.emulators.apple2)
  • Re: Seeking reverse-engineers - Apple II VisiCalc
    ... Right now this isn't possible because of the copy protection. ... It would be easy to have a web Apple II emulator so that any ... browser user could click on a link and run the original VisiCalc, ... required a DISK][. ...
    (comp.sys.apple2)
  • Re: transfering
    ... Jack Tseng wrote: ... I am wondering how to copy data from Apple II Disk drive to PC, to create the image dsk for Apple II emulator in what cable? ... the protection, ...
    (comp.sys.apple2)
  • Re: RFC : SOME IDEAS FOR THE APPLE II FPGAers
    ... but copying a 3.5" disk using the expansion RAM ... Apple II will disappear in the process, ... it emulate the noises :-) That would be cute. ... and use Copy II+ to rearchive them all from originals than it is to ...
    (comp.sys.apple2)