PAR Master code - why and how it works ?

[Madroms]

I understand how the other PAR codes work (codes started with 1, 3 and D), but I found no information on the master code. Does anyone have some information ? I am looking for technical information.

1) why is there a need for a master code ? What is its purpose ? Bypassing protection ?

2) what is the meaning of codes beginning with F and B ?

3) why some older version of PAR (v1.90 and above it seems) do need a different master code than later models ?

4) what are the differences between master codes found for different games:

- for the F codes: F6000914 C305, F6000924 C305, F601048A C305, F6000924 FFFF, F6000A04 FFFF,...

- for the B codes: B6002800 0000, B02FF800 0000, B60C2800 0000,...

5) why sometimes there is only the F code (also for later PAR), and why sometimes there are both F and B codes ? A mistake: B code always need to be entered with F code for later PAR models ?

6) And how to find them ? Other codes could be found with PAR+Commlink card or maybe using Yabause (any other ways ?), but the master code ?

Last question: I found some codes starting with 0. How do they work ?

Thanks.

 

[ExCyber]

http://wiki.yabause.org/index.php5?title=ActionReplay

 

[Madroms]

Ah great! Thanks

Give mostly all of the answers

So only questions 3) and 6) need an answer now.

For question 4), why some games need a different master code than the classic one ?

 

[Chilly Willy]

Ah great! Thanks

Give mostly all of the answers

So only questions 3) and 6) need an answer now.

For question 4), why some games need a different master code than the classic one ?

3 - Differences in how the cheat engine work determines the differences in the codes. You would need to know how the underlying mechanism works. As mentioned in the linked page, in general the console gets an interrupt, the code diverts it somewhere else where the cheat engine handles all the code actions, then jumps back to the original int handler.

6 - There are many guides on how to hack games. It's beyond the scope of the thread to cover that. Very generally, you reverse engineer the program to see how things are done, then use codes to change either code or data to do what you wish.

As for 4, it could be a number of reasons: maybe the original way of doing the cheats conflicted with code/data on certain games; maybe certain games do something (in the int handling) that conflicts with the cheat engine; and maybe some games look for the cheat engine specifically and do things to make it fail that need to be worked around. For example, on the N64 the Watch register is used to catch changes to the int handlers, so some games change WatchLo/Hi to make the cheat engine fail to catch where the int handlers are changed.

 

[Madroms]

Ok, thanks for the reply.

May I ask a last question: is it possible, with AR codes (a lot of them) to rewrite the memory where the ip.bin is loaded, before it is executed (with 0xxxxx code ?) just to change completely, or a part of, the ip.bin ?