Depending on the game/sdk, there are at least two. The checks are real close to eachother, you can see them if you compare a duplex eboot with an original one. Get the main check, then a few bytes further on, there's the second one.
Now the crap part, newer SDK has the 'nag you to death about updates' check(s) and those are trough the whole eboot. You know the screen that pops up suddenly during gameplay "an update is available, to continue blah blah must install bla bla?"
I don't really know ASM so i can't tell you how to find/patch those checks, but it would require a decent skilled hacker with IDA who works his way trough the whole binary. There's no string of code that you can just 'search & replace' for these newer checks/popups.. They use functions not available in older firmware.
These are the generic checks:
Code:
13 BC C5 F6 00 33 00 00 00 xx yy -> 13 BC C5 F6 00 33 00 00 00 34 00
13 BC C5 F6 00 00 00 01 00 xx yy -> 13 BC C5 F6 00 33 00 00 00 34 00
13 BC C5 F6 00 00 84 00 00 xx yy -> 13 BC C5 F6 00 00 84 00 00 34 00
13 BC C5 F6 00 00 90 00 00 xx yy -> 13 BC C5 F6 00 00 90 00 00 34 00
1B 43 4C EC 00 00 00 04 00 xx yy -> 1B 43 4C EC 00 00 00 04 00 34 00
The 1B 43 4C EC is the new one. This is usually found along with the popup/nag update thingy, which causes games to 'randomly freeze' during gameplay. (Sleeping Dogs, AC3 and Angry Birds trilogy have this for example. We can't fix those yourself easily.)