How did you guys find the Instruction Set of the Broadway Processor?

06-22-2012, 05:09 AM #1

Hey, I'm an aspiring programmer, and I was noticing that the CPU inside the wii is undocumented commercially (No publically released documentation on what hte OP codes are). Obviously to emulate the wii, you needed to code the Op codes in. How did you go about finding what each specific OP code was and what should go in the Instruction Register of the CPU? Did you use Jtag and try and decipher it through debugging?

Any information would be much appreciated!

**sktsqrl** · 06-22-2012, 05:11 AM #2

http://lmgtfy.com/?q=Instruction+Set+of+the+Broadway+Processor

**Squall Leonhart** · 06-22-2012, 05:15 AM #3

ninja skills and lots of liquor

06-22-2012, 05:16 AM #4

Okay, so I get that theres a manual for the processor. But what if there were no manual? Any ideas on how it could be done?

**NaturalViolence** · 06-22-2012, 08:50 AM #5

If there was absolutely no documentation at all and no major similarities to existing ISAs then all you would be able to do it play a long, tedious, and ultimately pointless guessing game.

**skid** · 06-22-2012, 09:53 AM #6

Broadway is a PowerPC processor with some extensions.

If the CPU is undocumented, write a lot of tests and note their results. This is how the DSP was emulated.

siferion · 06-23-2012, 05:56 AM #7

(06-22-2012, 05:16 AM)Magn3s1um Wrote: Okay, so I get that theres a manual for the processor. But what if there were no manual? Any ideas on how it could be done?

When I first found an NES cartridge with a serial interface in it I went to town poking an prodding with no technical documentation and only a mediocre understanding of CPUs. Took me months to figure out how many individual instructions existed, years to figure out what enough did to create a game around them (pong was my test). Eventually I posted my findings on a hardware hacking BBS and a bunch of other guys joined in whom were doing the same, before we knew it we had a very confusing mess that documented every last instruction.

Finding similar chips to the one your trying to understand goes a long way to solving all the headaches. If you can establish a minimum commonality then it allows you to write smart test that can save a lot of time otherwise spent reading debug spews.