Patapon 1 input lag (I want errrradicate it)

[LamerDrv]

So I searched "timing" code starting from z_un_0894BBC8 pointed by LunaMoo.

I climbed up the call stack to z_un_089510f0.
Here is pseudocode of z_un_089510f0:

Code:

drum_key = check_drum_key(); //read data from keyboard handling routines (return values:-1 if no key tapped, 1-"circle"; 2-"cross"; 3-"square"; 4-"triangle")
....
f0 = z_un_0887b068(); //is this "timing"?
...
z_un_089511e8(drum_key, f0, ...); //inside: if (drum_key!=-1 then bunch of code including z_un_0894bbc8 call

z_un_0887b068 returns fixed values in a circle:
0,0 (mathes "ideal drum strike" )
0,133333
0,266667
0,400000
0,533333
0,666667
0,800000
0,933333
0,933333
0,800000
0,666667
0,533333
0,400000
0,266667
0,133333

As far as I understand z_un_089510f0 is called regularly. And for one "tact" z_un_089510f0 must be called 15 times.

May be so-called "input lag problem" is the result of non-constant frequency of calls of z_un_089510f0 in the emulator?
I tried to log the calls of z_un_089510f0 (I used the memory access breakpoint for this - is this right ?). According to the log file in most cases the time between calls is 30-35 msec. But sometimes the time between calls drops to 12 msec or rises to >100 msec.

It's intresting... is there possibility to measure the time between calls of z_un_089510f0 on PSP?