Crack Down

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Crack Down, C64 version of the Sega arcade game: two agents, Ben and Andy, have to place time bombs in the enemy base and leave it before the time runs out.

Source 1

Property	Data
Title	Crack Down
Publisher and/or Developer	Sega
Year	1990
Disk(s)	1
Number of Index Holes	?
Media Type	5.25 DSDD
Retail, Budget or Compilation (with name)	Retail
Country of Release	US
Language(s)	English
Platform	C64
NTSC or PAL	NTSC
Protection	Manual Lookup
Working?	Yes
Archived	09 Mar 2013 sncboom2k
Verified by	enigma

• 
  Side 0

• 
  Manual check
• 
  Title
• 
  Game

sncboom2k: Sega (no photos).

The disk ("CRACKDOWN") shows the files "*" and "0" in the directory; the game is loaded with its own fast loader. The disk has no read errors.

The tracks 36 to 40 of side 0 and all tracks of side 1 contain no data, they are written with a continuous signal (only 1 bits). The game also starts from a copy without the tracks 36 to 40 (verified in VICE).

Streams

File:Streams CrackDown sncboom2k NTSC Sega.zip

G64

File:CrackDown sncboom2k NTSC Sega s0.g64

Disk side 1 is empty.

Disk Protection

After the start the game asks for a word from the manual ("Enter the word at the top left / top right / bottom left / bottom right of page 1 to 8"). The words are not stored on the disk: the routine at $C700 calculates a checksum over the entered word (start value $64, each character is shifted left by one bit and EOR-ed to the checksum) and compares it with the entry for the selected page and position in a table of 32 values ($C7AE) and with one additional value ($72, $C7CE) that is accepted for every question. After a correct word the loader is patched ($49 is written to $C1A4); after three wrong words the game continues without this patch and crashes with a black screen (verified in VICE).

Every entry with the checksum $72 is accepted for every question, for example "AJ" (verified in VICE) or "MAIN". Which word the developers intended for this value is not known, only the checksum is stored.

The manual that fits this check (at least 8 pages) is missing: no scan of the manual of this release is known. The instruction sheet of the European U.S. Gold release has only one page and does not fit.