N64 OP Codes? N64 Tracer?

gukingofheart · Feb 26, 2024

Know a website with the OPcode values? Here's one for the NES & SNES
http://www.6502.org/tutorials/6502opcodes.html
https://undisbeliever.net/snesdev/65816-opcodes.html

But I need one for the N64 with the numbers.
Do you know what 2400 means, I notice many different codes use this. is it a LDA? A NOP?

I have "Project64-v2.4.0-1688-ge230133", which has a debugger. Do you know if this emulator has a tracer or not? Or if I need some other emulator when it comes to tracing?
Tracing means, seeing all the debug data that ran before.

Any help, would be appreciated!

Mikemk · Feb 26, 2024

datasheet for the CPU: https://datasheets.chipdb.org/NEC/Vr-Series/Vr43xx/U10504EJ7V0UMJ1.pdf

Do you know what 2400 means, I notice many different codes use this. is it a LDA? A NOP?

The CPU architecture the NEC VR4300 was modified from is the VR4200, which is modified from R2400.

gukingofheart · Feb 26, 2024

Mikemk said:
datasheet for the CPU: https://datasheets.chipdb.org/NEC/Vr-Series/Vr43xx/U10504EJ7V0UMJ1.pdf

The CPU architecture the NEC VR4300 was modified from is the VR4200, which is modified from R2400.

Sure it's not a LDL, $24,3($0), or maybe it's a branch code.
Your sheet does not list the OPcodes, only the names.

Always Have 8 Red Coins On Bowser Levels
Action Replay/GameShark (this code uses a 2400, why?)
812F32E4 2400

Stepping Blocks Last Forever
Action Replay/GameShark (this code uses a 2400 & a 1000, why?)
812B18FC 2400
812B1904 1000

For NES & SNES, OPcodes have simple names like Load, Move, Copy, Branch.

bobmcjr · Feb 26, 2024

gukingofheart said:
Sure it's not a LDL, $24,3($0), or maybe it's a branch code.
Your sheet does not list the OPcodes, only the names.

Always Have 8 Red Coins On Bowser Levels
Action Replay/GameShark (this code uses a 2400, why?)
812F32E4 2400

Stepping Blocks Last Forever
Action Replay/GameShark (this code uses a 2400 & a 1000, why?)
812B18FC 2400
812B1904 1000

For NES & SNES, OPcodes have simple names like Load, Move, Copy, Branch.

These aren't necessarily writing opcodes. See this documentation on gameshark codes: https://en64.shoutwiki.com/wiki/Make_Nintendo_64_GameShark_Codes

The first code writes 0x2400 to address 0x2f32e4 constantly.

You'd need to check if this is overwriting code or just simply data. If it is overwriting code, keep in mind that N64 MIPS opcodes are 32-bit, so this 16-bit value would only be half an opcode, if it's even writing to an opcode. If it is, you'd need to find the full 32-bit value at that address (0x2f32e4) and either use a MIPS disassembler, or convert it to binary and read the ISA manual.

gukingofheart · Feb 26, 2024

Duh to myself, for not debugging after the cheat code is enabled.

It's an "ADDU" R0 R0 code.
Is R0 always set to 0. I understand more now, at least.
I'll just experiment with debugging different values, and write down the patterns

N64 OP Codes? N64 Tracer?

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Similar threads

Popular threads in this forum