59 lines
2.2 KiB
Plaintext
59 lines
2.2 KiB
Plaintext
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If you have Prince of Persia on 5.25", trade in for a 3.5". This is (or at least used to be) free. The 3.5" version is easy to deprotect:
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Prince of Persia 3.5" deprotect:
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Block: 7
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Byte: $16
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From: $90 (bcc)
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To: $80 (bra)
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Block: $A
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Byte: $8C
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From: $18 (clc)
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To: $38 (sec)
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This is to be used for archival purposes only.
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It'll work from a 800K RAMdisk with this deprotect. Probably also a 800K HD
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partition.
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Jay, krell@cornell.edu
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I don't question the availability for a crack, but, I do question Br0derbund's
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usage of a quarter track in Prince of Persia. I, too, received the program as a
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gift (I still fell that it kills IBM P.O.P.(not 2) w/o a SoundBlaster) and I
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immediately set out to make my legal backup.
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At least in version 1.0 (press CTRL-V during game play to check)
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there _IS NO_ quarter-track. You can tell
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quarter-tracks with true Apple Disk II drives. You can hear a slight tick
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instead of the chkkkkk....chkkkk....chkkkk normally heard when accessing
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track-to-track. I know this for a fact since this is how I detected the quarter
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track in AirHeart at 1B.25! In version 1.1 of P.O.P. there is the standard
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Br0derbund 'A5 96 BF' header and pitfully-easy-to-crack bitslip protection.
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Avoid the bit-slip routine by searching track #$00 on the boot side for E7 E7 E7.
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I used Copy II+ (yes, a legal copy!) for any backing up. Using a nibble editor
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replace the seventh occurrence of the E7 pattern with AF F3 FC EE E7 FC EE E7 FC
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EE EE FC. This routine will cooperate with //c's and IIgs' unlike the PARM in
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Copy II+ Plus designed to backup CrossWord Magic (backups won't boot except on
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//e's because of machine specific timings).
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Anyway .. .. .. that is the copy protection which exists on
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Prince of Persia. This same scheme occurs on Tetris
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from Spectrum Holobyte and Wings of Fury. Epyx also used the bit-slip timing in
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RoboCop, Ikari Warriors, California Games, World Games, Sub Battle Sim...
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etc...Br0derbund used it on Carmen Sandiego's (not W.I.T.W), Type!, and Animate.
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It was more fun to purchase the software just to crack it!
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Let me know if stand corrected about Prince of Persia's copy-protection.
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Michael Kelsey
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mkelsey@eecs.wsu.edu
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