Probability of Pre-emptive Attack on Bosses (FFVII)

[antd]

Does anybody know the probability of getting a pre-emptive battle against a scripted boss?

I'm currently using an automated script which tests entering the Guard Scorpion battle on different frames.
At the moment I have gone through 27,000 consecutive attempts at getting the preemptive attack, but it has not yet happened once.

I've read Terrence's Mechanics FAQ and it states, "You have a base chance of 16/256 of getting a Pre-emptive battle"

So my questions:

1. Is it just impossible to get a pre-emptive on Guard Scorpion? (a flag which forces a certain battle .ie, always side-attack, always 'normal' etc..)
2. Does the 16/256 base chance apply to bosses too? (that don't have the potential flag mentioned above)

[Terid__K]

I'm pretty sure it's only a few boss battles, like Jenova BIRTH.

[titeguy3]

And the turks. I've got a save file with a pre-emptive strike on the turks at the final midgar mission

[Kudistos Megistos]

There's a section in the scene.bin, at 0x0012 of the battle setup, that determines battle layouts such as "normal", "side attack" and "back attack". It may be useful to look at that section from Guard Scorpion to see whether it differs in any way from that of a battle that allows pre-emptive attacks.

There are a few other flags in the battle setup that aren't completely know yet, and it's very possible that something there may turn on or off that 16/256 possibility of getting a pre-emptive attack. I have suspicions about the escapable flag, which apparently contains other flags as well. I've noticed that most battles have FD, but most boss battles (including Guard Scorpion) have E9; a few battles that are unescapable (including the Turks in Midgar) have F9 (suggesting that there is a flag 0x40 is an escapable flag). It may be that there is also a flag here that can turn off the chance of a pre-emptive attack. (EDIT: disregard this; it seems that F9 is more common for boss battles and that the bit I thought was for pre-emptive battles actually turns something else on/off)

BTW, have you looked at the field script from that location? Or from places where you fight boss battles that do allow pre-emptive attacks? There may be something there that hasn't been documented yet.

[antd]

Hmm, no I have not. I'm using a PSX emulator.
Well, my script has now attempted over 70,000 attempts on Guard Scorpion. I think it's impossible.

[titeguy3]

Short answer. Yes. Yes it is. Unless you change it.

[willis936]

Hmm.

Jenova > several master pre-empt. materia > > profit

Also, I got a pre-emptive on the final Turks battle in the return to Midgar.
So it's possible at least on some of them.