Crazy Climber is one of my favorite games. However, there are a few things about the interface that I don't like:

Flaw 1.
When you put the game in Free Play mode, it just sits there with a static screen waiting for you to press a start button. It does not display the attract mode and the image burns onto your screen quickly if you leave the game on.

Flaw 2.
The default high scores when you turn on the game spell "Nichibutsu"... 10 letters. When you get a high score and it comes time to enter your name, you only get... 3 letters. Come on, people. You can obviously handle more than 3 letters if you can have "Nichibutsu" as a name! Besides, I tried the Japanese version of the game and it lets you enter 10. What a rip!

Flaw 3.
The method for entering your initials, frankly, sucks. You have two perfectly good four way sticks on the game, yet it only lets you move the cursor left and right and when you're all the way at the end around "Z", you have to scroll all the way up through 3 rows of letters if you want to enter an "A".

What to do about it.
I decided that, since 22 years have gone by and Nichibutsu has not released an update to fix these flaws, I could wait no longer. Something must be done about these things. If I were going to be able to truely enjoy the game, I'd have to do it myself.

The only problem is, Nichibutsu apparently didn't want folks mucking about with their program, so they encrypted their code and instead of a normal CPU, they used this weird looking green plastic block.

That block is a custom CPU module that decrypts the code ROMs. The good news is that someone smarter than myself figured out the encryption table and the details are in MAME's Crazy Climber driver source code. The bad news is that they only encrypted opcodes and not data. This means we can't just use MAME to dump out the decrypted code and burn a set of EPROMs and install them on the board. The only way MAME knows what values are supposed to be opcodes and which are supposed to be data is to actually run the code. What they do is create a memory region that's twice as big as the code ROMs and fill one half with the decrypted data and the other half with untouched data. When MAME runs the game, if it's executing an opcode, it reads from the decrypted region and if it's reading data, it reads from the untouched data. In order for us to do the same, we'd have to burn a set of EPROMs that are twice the size of the original and connect the "M1" pin of the Z80 CPU to the highest address pin of each EPROM. This works because when the CPU is executing an opcode, the M1 pin will be "low" and when it is reading data, it will be "high" (or the other way around, I forget), so you use that to switch between the upper and lower halves of the data in the EPROMs.

Well, I didn't much like the idea of running wires all over my PCB. But, the only way to get a correctly decrypted set of ROMs the same size of the original would be to somehow play through the game and monitor what gets used as what. You could modify MAME to create a log file indicating what values were used as what. However, you'd need to play through the entire game,trying to get every last byte to be read to be 100% sure you've got the two regions merged correctly. This is near impossible to do by just playing through the game, since there will be bits you will miss no matter how many times you play. I got into a bit of discussion on this topic with David Widel, who had been trying this technique with some other games and couldn't get more than about 93% of a game's ROMs identified with this method. I had some ideas of my own on how to get 100% identification, so he sent me his modified version of MAME and I went to work on my favorite encrypted game... Crazy Climber.

There are two types of data that a given byte can be. The first type is data associated with an opcode.
Here is an example of the first type:

CA C9 0B -- jp z,$0BC9

CA is the opcode (jp z or jump if zero) and C9 0B is the data (the address to jump to, 0BC9).

The second data type is data that is read in chunks, like text strings, level layouts, etc.

After playing through the game a couple times to get a good sampling to work with, and looking at all the places that weren't getting executed, I noticed that all of the second data type in Crazy Climber was enclosed with a header and footer that was the same every time...

C7 FB [DATA] C7 F3.

Bingo! That meant that I would be able to identify every single byte in the game without playing it at all. However, I was actually kinda having fun figuring out how to get all the code in the game to execute, so I went ahead and went through all the code using my newfound information to accurately target the areas I needed to get executed, setting breakpoints at key locations and figuring out the conditions that would be required to run that chunk of code. It took about 8 more hours of fiddling to get to 100% identification. Along the way, I found almost all the interesting bits of code and memory locations that I'd need to twiddle to make my mods to the game to fix the interface flaws I felt it had. (Check out the bottom of the page for some of the interesting areas I found.) So, the result of this is we now have decrypted code that is easy (realatively speaking) to modify to our (well, at least to my) liking. The EPROMs with encrypted code can be replaced with EPROMs containing non-encrypted code and the funny green block can be replaced with a standard Z80 CPU. Sounds grand, but there's one problem... the socket the green block plugs into is not a standard CPU socket. In order to run unencrypted code on an original PCB, you will need to make an adapter.

I started with one of those little blank PCBs from Radio Shack, bought a 40 pin wire wrap socket and a 40 pin machine pin socket and went to work.

The existing socket is a 40 pin custom connector similar to an IDE connector on a hard drive. I cut the center plastic braces of the wire wrap socket and flipped the two sides around so they would fit right next to each other on the blank PCB and match the spacing of the "IDE" connector. The pinout is a pin for pin match of a Z80, so it's not too hard... It went from this:

>||           ||          ||        ||

to this:


Then I cut the center plastic braces on the machine pin socket the same way and placed the rows on either side of the wire wrap socket, and connected the two sets of pins, like so:

 | | | | | | | | | | | | | | | | | | 
 | | | | | | | | | | | | | | | | | | 

The wire wrap legs sticking through the bottom of the PCB plug into the "IDE" socket.

A standard Z80 CPU fits into the outside rows.

I used the original nuts and bolts from the green block to secure the new PCB.

All done. This board will now run a set of standard sized, unencrypted ROMs (provided you haven't plugged the CPU in backwards). See below for a download link.

Fix 1.
Whew. Now that that was all done, I set about making my changes to the code. I started with the Free Play mode. I first disabled the existing Free Play code and found some unused areas to write my own routines. I made it so that if the Free Play dip switches are on, if you press one of the start buttons at any time, it'll add the appropriate amount of credits and start a game. I also changed the attract mode during the high score display to tell you Free Play mode is on and lengthened the time the high scores are displayed slightly. Here's my new code with comments so you can follow what I did:

So, now the game will display the attract mode when Free Play is on, greatly reducing the chance of burning an image on your CRT.

Fix 2.
Next was the number of characters for the high score. That part was real easy. All I had to do was change the $03 at location $0C8A to a $0B.

Fix 3.
Lastly, I needed to fix the high score inital entry routine to be easier to navigate. Here's my new code with comments so you can follow what I did:

That makes it so if you press down on the left stick, the cursor moves, down, press up and it moves up. If you press left while the cursor is on "A", it scoots down to "END" and if you press right on "END" it goes up to "A". Ahhh... much better! You can download ROMs with these patches already made from the download area at the bottom of the page.

Here are some interesting areas I found while poking around:

Location Description
00EA Adds four credits if Free Play is on
01BE Code that checks to see if you're playing when a credit is added
03A7 Code that determines the number of lives in game
03C1 Code that determines the score needed to win an extra life
03E2 Code that determines the credits per coin (04 was Free Play)
0402 Code that determines the coins per credit
0432 Adds four credits if Free Play is on
058F Code for accepting credits and starting a game
05E8 Code for a delay
0611 Code to detect start buttons being pressed
07F4 Code that displays the title screen
0A0D Code that writes "FREE" on the screen
0A5B Code that writes "Push 1 or 2 Players Button" on the screen
0BB3 Code for entering high score initials
0C8A Number of characters for high score initials
0DA8 Easter Egg! If you entered "JORDAN.LTD" as your high score initals it chops off the ".LTD" part and adds two credits. However, since they cut the number of characters you can enter in the US version down to 3, there's no way to enter 10 initials. Only the Japanese version will let you. Go ahead and try it on the US version with my hack to let you enter 10 letters.
0E37 Code that displays the high score table
80D9 Memory location holding your current score
80D3 Memory location holding the current number of lives during play
807A Memory location holding the number of credits per coin
8075 Memory location holding flag that says if a game is in progress
8072 Memory location holding the number of credits
8095 Memory location holding high score table
8080 Memory location holding flag that says if it's a 1 or 2 player game


Decrypted US version of Crazy Climber to use on a PCB with a standard Z80 in place of the green plastic block.
Includes 5 new ROMs. CC11, CC10, CC9, CC8 and CC7. Decrypted US version with my mods applied.
Includes 5 new ROMs. CC11, CC10, CC9, CC8 and CC7. Consider these mods beta.

Encrypted US version with my mods applied. For use on a PCB with the original green platic block still there. Consider these mods beta.
Includes 2 new ROMs. CC11 and CC7.

If you need to yell at me, email me at

I made these patches because I enjoy figuring out how to do them and I really wanted to see these improvements made to the game. I don't expect to make a bunch of money from them, so they're free for downloading. If you decide you want to sell them to folks, please only charge for the cost of the blank EPROMs and shipping. I wouldn't appreciate you making a profit from my work.