Michael J. Mahon wrote:
Mark McDougall wrote:mdj wrote:Not sure of how such things were done, but the PC drive is somewhat more 'intelligent' that the Apple II unit, and essentially incapable of writing 'bad' data by itself. The Apple II's essentially 'soft' design means that much lower level disk information is software visible. The upshot of this being that any erroneous data that could be written by some as yet undiscovered disk duplicator could be approximated by an actual Apple II drive.I seem to recall a rumour that the disk surface was damaged by a laser. Consider this: a protection scheme that does indeed permanently damage a known set of bytes on the disk surface. The software boots and then writes data to the area known to be 'bad'. Then it reads it back, and verifies that the data does *NOT* match what was written. This scheme could NOT be duplicated on any Apple II disk drive, regardless of the level of control over the drive itself.You are correct. This technique was used on some PC titles, but I'm unaware of it ever being used on an Apple II title (too late and too expensive). Does anyone know of an Apple II title that was distributed on disks with "precision physical damage"?
Well, I don't know if this is urban legend but this was talked about as a very hard to beat copy protection and it was supposed to be Apple2:
They would put a hole in the disk, not precision but just in a general area so it didn't damage data. The affected tracks would read in such a way that the hole was detected as nothing while a copy would read differently. Even if you reproduced the hole in the copy; the program would see the hole ok but it would also detect the hole in the data left by the original hole...
Reminds me of a program that detected me when I was using a debugger to find out how to patch the program to get rid of an unwanted poppup screen (on pc). At the bottom of the screen came a black text on yellow background saying 'It is illegal and unethical to tamper with out copyright notice' (I think). I hit the powerswich as fast as I could. Fortunately it wasn't nasty or didn't have time enough, it did nothing more than that. I did hack the poppup though. When we later bought the next version we paid extra to get it without the poppup. :-)
-- Knut (delete 'nogarbage.' for email)