EASY WAY TO FIND SOME DATA IN NES ROMS ----------------------------------------- Did I say easy. Ya that's right I did ^_^ . There is a way to find the pattern tables, name table(possibly level data), attribute tables, And palettes. All you do is fire up the NES emulator Nesten. Go to View then to the debugger. And make sure your in the right area in the game you want to locate the data for. Then dump the PPU. PPU is Picture Processing Unit for short. Ok you have a nice and somewhat smaller file to mess with. Where do you start well I will explain. The PPU file you dumped is divided into sections. What I am going to do is present the following table for you to look at. And by the way this table is lifted nearly verbatim from Yoshi's Nintendo Entertainment System Documentation. Programmer Memory Map +---------+-------+-------+--------------------+ | Address | Size | Flags | Description | +---------+-------+-------+--------------------+ | $0000 | $1000 | C | Pattern Table #0 | | $1000 | $1000 | C | Pattern Table #1 | | $2000 | $3C0 | | Name Table #0 | | $23C0 | $40 | N | Attribute Table #0 | | $2400 | $3C0 | N | Name Table #1 | | $27C0 | $40 | N | Attribute Table #1 | | $2800 | $3C0 | N | Name Table #2 | | $2BC0 | $40 | N | Attribute Table #2 | | $2C00 | $3C0 | N | Name Table #3 | | $2FC0 | $40 | N | Attribute Table #3 | | $3000 | $F00 | R | | | $3F00 | $10 | | Image Palette #1 | | $3F10 | $10 | | Sprite Palette #1 | | $3F20 | $E0 | P | | | $4000 | $C000 | F | | +---------+-------+-------+--------------------+ C = Possibly CHR-ROM N = Mirrored (see Subsection G) P = Mirrored (see Subsection H) R = Mirror of $2000-2EFF (VRAM) F = Mirror of $0000-3FFF (VRAM) You see this table. Well you can take each area in the PPU file that you dumped and possibly find the data in the rom if the data is not compressed or using some other odd type of data storage commonly used with some mappers. What you do is take about a dozen or so bytes from the PPU file and use the search function in most hex editors to locate the bytes in the rom that you want to find the data. And once you find a match you simply look at the surrounding data to make sure it matches up properly. 1.)Pattern Table #0 This is the current pattern table loaded. This could be sprites or background or both. This table is usually background tiles. The size of this section is $1000 in hex or 4KB which is half of the standard 8KB of CHR. This is the data that you can view in a tile editor. This may be usefull if you want to make a program to edit tiles. This is what you see in the Nesticle tile editor. This is the first half of the table. 2.)Pattern Table #1 This is the second half of the pattern table that is currently loaded and is the same size as Pattern Table #0. This table usually contains sprites. 3.)Name Table #0 Ok here is the Name Table #0. This section is what contains your tile map data. Like for title screens, non scrolling one screen overhead maps, And also is used for parts of scrolling maps that is combined with the other name tables when using mappers. This table is 960 bytes large. 4.)Attribute Table #0 Ok this is sorta a tricky one to explain. You ever edited a screen and you ran into one where you changed a tile and it ended up NOT being the color you wanted. well Attribute Tables have something to do with that. Each byte in this table controls the current 4 color set used from the 16 byte palette. Thus if you change certain bits in the byte this will control what colors from the palette will be used for a 4x4 section of tiles. Yes that's 16 total tiles. Attribute tables are sorta limited as you have to use only 4 colors for a entire 4 tile section. Thus you can change any 4 tile section to a different color set if you wish. I did this with the Asmik Kun overhead map to expand the signs. Also I am going to paste in here a table from the Nintendo Entertainment System Documentation once again to give you a visual demonstration. It's quite confusing; two graphical diagrams may help: +------------+------------+ | Square 0 | Square 1 | #0-F represents an 8x8 tile | #0 #1 | #4 #5 | | #2 #3 | #6 #7 | Square [x] represents four (4) 8x8 tiles +------------+------------+ (i.e. a 16x16 pixel grid) | Square 2 | Square 3 | | #8 #9 | #C #D | | #A #B | #E #F | +------------+------------+ The actual format of the attribute byte is the following (and corris- ponds to the above example): Attribute Byte (Square #) ---------------- 33221100 ||||||+--- Upper two (2) colour bits for Square 0 (Tiles #0,1,2,3) ||||+----- Upper two (2) colour bits for Square 1 (Tiles #4,5,6,7) ||+------- Upper two (2) colour bits for Square 2 (Tiles #8,9,A,B) +--------- Upper two (2) colour bits for Square 3 (Tiles #C,D,E,F) Ok and this ends the visual. The size of the attribute table is 64 bytes large and the byte that controls the first 4x4 tile section starts at the top of the screen starting from the left and it goes to the right untill you end at the far right side and you go to the next level below that and once again to the left and work to your right. Now here is a much larger visual that I am going to attempt to give a better understanding of the table. The entire table covers 32x30 tiles or 256x240 pixels. This differs from PAL to NTSC resolution. TOP OF SCREEN +----------+----------+----------+----------+----------+----------+--------------------------------- | 4X4 Tile | 4X4 Tile | 4X4 Tile | 4X4 Tile | 4X4 Tile | 4X4 Tile | | section | section | section | section | section | section | | 23C0 | 23C1 | 23C2 | 23C3 | 23C4 | 23C5 | +----------+----------+----------+----------+----------+----------+ | | | | | | Also keep in mind that attribute tables are disabled by some mappers like MMC5 for instance. So you may not find them. This raps this section up. I might finish the table in the future perhaps. 5.)Name Table #1 This is one of the many mirrored sections of NES games. Most always this data is exactly the same as Name Table #0. This section can be used by mappers. However you should examine this area for data. 6.)Attribute Table #1 This is another mirrored section from the attribute table #0 7.)Name Table #2 This is also another mirrored section. 8.)Attribute Table #2 Mirrored section 9.)Name Table #3 Also a mirrored section 10.)Attribute Table #3 Also a mirrored section 11.)Image Palette #1 This is the 16 byte palette used for background graphics and this palette is usually for the section in the game that you want to hack. 12.)Sprite Palette #1 This is the 16 byte palette used for sprites. And once again is usually used for the section you want to hack. The point to this doc is that I tried to explain how you can find areas in your game that you want to hack. Doing this may save you hours of work. All you have to do is find the general area write that down. And then you use a table for palettes and you can easily tell what is what in only 16 bytes. For the larger areas like name tables you simply write down the area and you may use Nesticle to get the tile index numbers and search in that area. Keep in mind the area may still use some type of RLE compression and some other wierd ordering. However it is alot easier to deduce the exact location. Note:About the name tables. It is good to search them all for screens that scroll in any direction or even in all directions. This about raps this document up. However just one last note. This isnt a sure fire method of finding data. However I have found data more times then not using this method and in less time. Also this document is not aimed to be technical at all but more to help rom hackers. Contact Info -------------- You can contact me Gil_Galad75@hotmail.com for any questions or comments. Constructive advice is much better recieved. Thanks for reading and hope this helps you out. Credits --------- Thanks goes to in no particular order. Yoshi for his NES Tech doc, All others for the previous research, Keven Horton because one day I was hacking the Asmik Kun overhead map and ran into the problem of the different colors and then after reading Yoshi's NES Tech doc I figured out that I needed to change the attribute table and I noted the location of the table in memory. however I didnt know how to locate the attribute table in the rom so I asked the channel and Keven told me to dump the PPU in Nesten and that got the ball rolling so to speak. So thanks to him.