| Mega Man's cartridge ROM, counted by part of the game: each stretch of code or data goes to the part the disassembly's labels and comments say it serves, and the value sums the bytes of each part. | 0x10-0x2000f | Code notes |
Mega Man 2's sound engine entry and channel setup are Mega Man's, with two changes: _music_fade_in_out no longer ignores a new fade while one is running, and where Mega Man steps X with INX, four operands use an address plus 1 instead and one writes SQ1_SWEEP plus X. The engine starts at $8000 instead of $9000, so its jump and call addresses differ too. | 0x11010-0x1124e | Code |
Mega Man 2's per-frame channel update is Mega Man's, except that _break_frame and the end of _pitch_envelope_common address the next APU register as SQ1_SWEEP plus X, where Mega Man steps X with INX and writes SQ1_VOL plus X. The code sits $100A lower, so its jump and call addresses differ too. | 0x1124f-0x11588 | Code |
| Mega Man 2's sound effect reader is Mega Man's, instruction for instruction and with the same RAM, moved $100C lower: only its jump and call addresses and the addresses in its command table differ. | 0x11589-0x116cf | Code |
| Mega Man 2's song data reader is Mega Man's, instruction for instruction and with the same RAM, so the two games read the same note and command format. It sits $100C lower: only its jump and call addresses, its command table, and the address of the note table differ. | 0x116d0-0x11990 | Code |
Mega Man 2's note length and pitch tables are Mega Man's but for one pitch: the period of the note the disassembly names nEb1 drops from $059E to $0594, about 12 cents higher (computed). The region also ends with 3 bytes of $FF filler instead of 7. | 0x11991-0x11a6f | Code |
Mega Man 2's _joy is Mega Man's, line for line; only the two button bytes it writes moved in zero page, from $14 and $18 to $23 and $27. | 0x1d59d-0x1d5ba | Code |
Mega Man 2's _object_tiles_update is the loop Mega Man enters at _init_object_tiles, which copies the tile buffer to CHR RAM, with its RAM at new addresses. Mega Man 2 drops the test in front of it and the _object_tiles_update_yellow_devil path, which writes two bytes at each of several PPU addresses, a row ($20) apart. | 0x1d5bb-0x1d619 | Code |
Mega Man 2's _scrolling_vertical follows Mega Man's _scrolling_up_down: the same name table and attribute address math and the same loop writing four 8x8 tiles per 16x16 quarter. Mega Man 2 computes the 32x32 block's address from the screen number, where Mega Man looks the screen up in a pointer table and checks _special_blockset_collision for a block the disassembly labels removed; some of its RAM moved too. The rest of each region is different code. | 0x1cf33-0x1d075 | Code |
Mega Man 2's _nmi_wait_0e and _nmi_wait_0d keep the steps of Mega Man's _nmi_wait: save the last buttons, wait for the NMI, call _joy, and mark the newly pressed buttons. The two differ only in the bank they map at the end, and each first calls _background_palette. Mega Man 2 drops the path for buttons the game forces and moves the water frame into _nmi_wait_water. | 0x1c02b-0x1c069 | Code |
Mega Man 2's death explosion takes its twelve pieces' x and y speeds and facing flags from five 12-byte tables identical to Mega Man's explosion tables. The code around them is new: Mega Man's _create_explosion_object sets up one piece per call, and Mega Man 2's _create_explosion loops over all twelve. | 0x1f89a-0x1f8d5 | Code |
Both games' bank switch routines map a PRG bank at $8000, but Mega Man 2's is new code for a different board: Mega Man writes the bank number once, to its own byte of a bank table (the disassembly's uxrom_prg_bank), and Mega Man 2 writes it to MMC1 one bit at a time, then runs any sound an NMI put off during the switch. | 0x1c3ac-0x1c3ce | Code |
| Both games' stage loops run a frame of play and wait for the NMI, but Mega Man 2's is new code: it calls its own routines in its own order, opens the menu on Start with no Select pause, and waits an extra frame now and then in water. Its region also starts the stage before the loop. | 0x1516e-0x15216 | Code |
| The last 16 screens of Metal Man's map, $1C to $2B (1,024 bytes), are byte for byte the last 16 of Mega Man's Cut Man and Wily stage 1 map: Cut Man's screens $0C to $0F and Wily stage 1's $10 to $1B. Metal Man's screens $18 to $1B repeat four of them, Wily stage 1's $18 to $1B. | 0x7d0-0xbcf | Code |
| Tiles 1 to 84 of Mega Man 2's title screen patterns (1,344 bytes) are byte for byte tiles 1 to 84 of Mega Man's. | 0xe820-0xed5f | Code |
| Mega Man 2's six menu border tiles, the end of its common stage tiles, are Mega Man's six menu tiles, byte for byte. | 0x3610-0x366f | Code |
| Mega Man 2's five READY letter tiles have Mega Man's letter shapes, row for row, but in each tile's second bit plane instead of its first, so the letters draw in color 2 of their palette where Mega Man's draw in color 1. | 0x3670-0x36bf | Code |