Boulder Dash (NES)/ROM map

The following article is a ROM map for Boulder Dash (NES).

Addresses

• 0x2773 = Rockford Palette Selection
• 0x2931-0x2938 = World 1 Password Data
• 0x2939-0x2940 = World 2 Password Data
• 0x2941-0x2948 = World 3 Password Data
• 0x2948-0x2950 = World 4 Password Data
• 0x2951-0x2958 = World 5 Password Data
• 0x2959-0x2960 = World 6 Password Data
• 0x2961-0x2968 = World 7 Password Data
• 0x2969-0x2970 = World 8 Password Data
• 0x2971-0x2978 = World 9 Password Data
• 0x2979-0x2980 = World 10 Password Data
• 0x2981-0x2988 = World 11 Password Data
• 0x2989-0x2990 = World 12 Password Data
• 0x2991-0x2998 = World 13 Password Data
• 0x2999-0x29A0 = World 14 Password Data
• 0x29A1-0x29A8 = World 15 Password Data
• 0x29A9-0x29B0 = World 16 Password Data
• 0x29B1-0x29B8 = World 17 Password Data
• 0x29B9-0x29C0 = World 18 Password Data
• 0x29C1-0x29C8 = World 19 Password Data
• 0x29C9-0x29D0 = World 20 Password Data
• 0x29D1-0x29D8 = World 21 Password Data
• 0x29D9-0x29E0 = World 22 Password Data
• 0x29E1-0x29E8 = World 23 Password Data
• 0x29E9-0x29F0 = World 24 Password Data
• 0x3876 = World 1-1 CHR Bank for Level Data
• 0x3877-0x3878 = World 1-1 Level Data Pointers
• 0x3879 = World 1-2 CHR Bank for Level Data
• 0x387A-0x387B = World 1-2 Level Data Pointers
• 0x387C = World 1-3 CHR Bank for Level Data
• 0x387D-0x387E = World 1-3 Level Data Pointers
• 0x387F = World 1-4 CHR Bank for Level Data
• 0x3880-0x3881 = World 1-4 Level Data Pointers
• 0x3882 = World 2-1 CHR Bank for Level Data
• 0x3883-0x3884 = World 2-1 Level Data Pointers
• 0x3885 = World 2-2 CHR Bank for Level Data
• 0x3886-0x3887 = World 2-2 Level Data Pointers
• 0x3888 = World 2-3 CHR Bank for Level Data
• 0x3889-0x388A = World 2-3 Level Data Pointers
• 0x388B = World 2-4 CHR Bank for Level Data
• 0x388C-0x388D = World 2-4 Level Data Pointers
• 0x388E = World 3-1 CHR Bank for Level Data
• 0x388F-0x3890 = World 3-1 Level Data Pointers
• 0x3891 = World 3-2 CHR Bank for Level Data
• 0x3892-0x3893 = World 3-2 Level Data Pointers
• 0x3894 = World 3-3 CHR Bank for Level Data
• 0x3895-0x3896 = World 3-3 Level Data Pointers
• 0x3897 = World 3-4 CHR Bank for Level Data
• 0x3898-0x3899 = World 3-4 Level Data Pointers
• 0x389A = World 4-1 CHR Bank for Level Data
• 0x389B-0x389C = World 4-1 Level Data Pointers
• 0x389D = World 4-2 CHR Bank for Level Data
• 0x389E-0x389F = World 4-2 Level Data Pointers
• 0x38A0 = World 4-3 CHR Bank for Level Data
• 0x38A1-0x38A2 = World 4-3 Level Data Pointers
• 0x38A3 = World 4-4 CHR Bank for Level Data
• 0x38A4-0x38A5 = World 4-4 Level Data Pointers
• 0x38A6 = World 5-1 CHR Bank for Level Data
• 0x38A7-0x38A8 = World 5-1 Level Data Pointers
• 0x38A9 = World 5-2 CHR Bank for Level Data
• 0x38AA-0x38AB = World 5-2 Level Data Pointers
• 0x38AC = World 5-3 CHR Bank for Level Data
• 0x38AD-0x38AE = World 5-3 Level Data Pointers
• 0x38AF = World 5-4 CHR Bank for Level Data
• 0x38B0-0x38B1 = World 5-4 Level Data Pointers
• 0x38B2 = World 6-1 CHR Bank for Level Data
• 0x38B3-0x38B4 = World 6-1 Level Data Pointers
• 0x38B5 = World 6-2 CHR Bank for Level Data
• 0x38B6-0x38B7 = World 6-2 Level Data Pointers
• 0x38B8 = World 6-3 CHR Bank for Level Data
• 0x38B9-0x38BA = World 6-3 Level Data Pointers
• 0x38BB = World 6-4 CHR Bank for Level Data
• 0x38BC-0x38BD = World 6-4 Level Data Pointers

Disassembly

Password Comparison Routine

This fragment of code compares the input password with the passwords of all 24 levels of the game.

00:A8BA:A9 00     LDA #$00
00:A8BC:85 67     STA $0067   // Reset level counter
loop:
00:A8BE:A5 67     LDA $0067   // Load level counter
00:A8C0:0A        ASL
00:A8C1:0A        ASL
00:A8C2:0A        ASL
00:A8C3:AA        TAX         // Level password character counter X:= A * 8
00:A8C4:A0 00     LDY #$00    // Reset input password character counter
passwordCompare:
00:A8C6:B9 4D 00  LDA $004D,Y // Load Ath character from input password at $004D
00:A8C9:DD 27 A9  CMP $A927,X // Compare to level passwords at $A927.
                              // Data structure: [Lvl 1 password (8bytes)][Lvl 2 password (8bytes)]…
                              // Only the first 6 bytes are used, see below.
00:A8CC:D0 09     BNE $A8D7   // If not equal, goto nextLevel
00:A8CE:E8        INX         // Increment level password character counter
00:A8CF:C8        INY         // Increment input password character counter
00:A8D0:C0 06     CPY #$06    // Check if password length of $06 characters is reached
00:A8D2:90 F2     BCC $A8C6   // If not, goto passwordCompare
00:A8D4:4C E2 A8  JMP $A8E2   // Comparison finished, current level password matches input password. Goto passwordCorrect.
nextLevel:
00:A8D7:E6 67     INC $0067   // Increment level counter
00:A8D9:A5 67     LDA $0067
00:A8DB:C9 18     CMP #$18    // Check if last level was reached
00:A8DD:90 DF     BCC $A8BE   // If not, goto loop
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