The following data is comprised of ROM and RAM finds that I figured some on this message board would fancy. http://pastebin.com/qHMW7B9F
The following was done by various members of an IRC called #.blank. Which can be found on the Rizon network. (Note, you you can trace RAM addresses to ROM though the DMA controller of course) You can find us here as well: http://pb.ajf.me/

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Tools (To get started, at least)
The ROM addresses that you see can of course be worked with with a hex editor, however, you can also view the locations in MIPS source/disassembled code rather than ol' base16 strictly, at least.

http://nemu.emuunlim.org/ Nemu64. An emulator that has tons of debugging features but hasn't been worked on in over a decade and is relativity buggy but is still, by far, your best option for the content I have displayed here.

https://gzrt.googlecode.com/files/n64tree-win32-v1.0.7z For assembling gameshark codes in C
Tutorial applicable to the toolchain:
https://code.google.com/p/gzrt/wiki/Nintendo64ToolchainSetup Setting it up

http://www.romhacking.net/utilities/210/ LemASM is an assembler/dissembler and ROM editor which also allows hex view
http://www.romhacking.net/forum/index.php?topic=18868.a0 A better program than LemASM and could become your best friend

http://viper.shadowflareindustries.com/files/hax0r/renegade64v17.rar Renegade64 can hook to any N64 emulator and is a capable of assembling MIPS R4300i code to into gs code format, memory scanning and other things you can figure out on your own.
http://viper.shadowflareindustries.com/files/hax0r/renegade64v17_src.rar Source

There are tutorials below for everything I posted above!


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Guides/Tutorials
Desire to learn how you can make use of this newly acquired knowledge? Here I give you a list that I compiled with practical, informative tutorials, guides, references, etc:

http://n64devkit.square7.ch/ Every Nintendo 64 programming manual (excluding games, including 64DD). Excellent resource
http://groups.csail.mit.edu/cag/raw/documents/R4400_Uman_book_Ed2.pdf R4000 manual
http://www.mrc.uidaho.edu/mrc/people/jff/digital/MIPSir.html ISA
https://github.com/mikeryan/n64dev/tree/master/docs/n64ops Opcodes (A lot more can be found by navigating back to the n64dev directory)

Want stuff with more layman's terms and hands on/practical?

These first two I assume will be of much avail for beginners.
http://sm64-hacks.square7.ch/mips3.pdf Practical usage
http://www.chortle.ccsu.edu/assemblytutorial/index.html An amazing MIPS course
First off, I recommend the above for everyone, noob or not. The former is the most "practical" guide of the bunch that I keep blabbing on about; the latter is a college course on MIPS. Those two should work perfectly.

Moreover, I still provided more links just in case.


http://www.smwcentral.net/?p=viewthread&t=68900 SM64 Hello world with MIPS hacking
https://www.youtube.com/watch?v=jS-w20Dbnd8 Introduction to LemASM
http://orbitaldecay.com/N64/index.html Learning basic debugging tool usage and a very basic introduction to assembly (Is also quite good)
https://sites.google.com/site/flotonic65/modding/n64zeldatut/startasm A brief, but not well explained, tutorial for tracing basic arithmetic operations and making a gs out of assembly
http://viper.shadowflareindustries.com/index.php?doc=n64asm An old practical, informative tutorial to Nintendo 64 hacking
http://doc.kodewerx.org/hacking_n64.html In depth gameshark code creating guide
http://glitchkill.proboards.com/thread/5851/oot-mm-hacking-asm Practical OoT tutorial for making gameshark codes with c
http://www.smwcentral.net/?p=viewthread&t=69589 Same as above, but for Super Mario 64 and more explanatory
http://patater.com/gbaguy/n64asm.htm Yet again more practical tutorials on some daily planner looking system


I cannot link to ROMs for legal reasons and the terms and conditions of this site. You can find them yourself easily through Google.