I've reverse engineered the real Z axis limit for the vertex data and apparently this is a widely used limit in several PSP functions.
Also, this was probably the reason why so many recent games weren't able to display graphics. Apparently, a particular japanese engine makes a small mistake by instead of setting the nearz and farz parameters to 10000 and 50000 (which are the most common values used by devs), sets the first value to 100000 (out of range).
I still haven't changed the optimized reading because, like kytoxid stated, forcing it may not be the best solution, but I'm currently checking why this isn't producing the proper results.
Also, this was probably the reason why so many recent games weren't able to display graphics. Apparently, a particular japanese engine makes a small mistake by instead of setting the nearz and farz parameters to 10000 and 50000 (which are the most common values used by devs), sets the first value to 100000 (out of range).
I still haven't changed the optimized reading because, like kytoxid stated, forcing it may not be the best solution, but I'm currently checking why this isn't producing the proper results.