ASUS P3B-F have dynamic voltage regulation which depends on CPU you've installed.

Thanks for fast reply, so after installing my tualeron it will just automatically lower voltage right? Also is it possible to run that 1.2 tualeron on 133.3 FSB which would result in 1.6 Ghz clock?

Yes, motherboard will lower your voltage options accordingly. Possible, but not guaranteed.

But what if it won't lower, will tualatin fry when entering BIOS on 2.0V, or it will handle it for some time allowing me to check what voltage have been set.

The voltage should not allow being changed via the BIOS when the 'JEN' jumper is set to Jumperfree. See page 20 of the manual.
Maybe you should check out if the board + slotket behave correctly by running <1.8volt Coppermine cpu on that slotket before you install a Tualatin.

Unluckly i don't have coppermine, But i tried with PII deutsches and i also couldn't set lower than 2.0V. Parke right now i am at jumperfee setting (JEN 2-3), should i change it?

When the JEN is set to jumperfree the board will automatically set fsb and voltage according to the cpu that is installed. If you want to experiment you -have- to use the 'MANUAL' mode, thus you then have to set the fsb via the blue dipswitch (switches 7-10) on the board and then you should be able to adjust the voltage via the BIOS. (You do not have to change the switches (1-4) for frequency multi because all these cpu's are 'locked' and switches 1-4 do not have any effect). But if this is all new to you I still advise to first try it out with some cheap Coppermine before you proceed.

So the best option is now to try manualy set my Katamai to 1,9V just to check if jumpers allow me to do it. You are right i'm not familiar with jumpers. I'm not form this generation, but i bought that tualeron for 5$ so i will just take the risk. But for me this is odd that i cant set lower voltage without maniupulating with jumpers. But there is one more thing, i updated my bios version from 1003 to 1008 beta with additional tualatin microde. To update bios on this motherboard you need to use floppy with ms-dos, unluckly my floppy drive is broken. So i rebooted my 98se to dos mode, and aflash let me to update bios without boot block and escd. Maybe with newer boot block comes more in bios voltage regulation options?

When you have set the JEN jumper to MANUAL and the fsb dip switches to the setting for fsb 100 you should theoretically be able to change the voltage in the BIOS to see if at least that part works ok.
These ASUS BIOS updates, for as far as I know, do not change options for voltage regulation but they do contain microcode for the later/latest cpu's so that the voltage that is proper for the installed cpu can be applied. I have a similar board as yours, revision:1.03 with a 'new' VRM HIP6020ACB and I run a 1000Mhz Coppermine Celeron on it at 1.75volt which is automatically detected.
The reason why I advise to first try out if it works ok is that -if- there is a problem with the detection of the right voltage it is possible that the board starts up with maximum voltage and then it is possible that your Tualatin is instantly fried. These boards are now almost 20 years old, and so are the slotkets, and we cannot expect them to keep functioning properly forever.... right ? 😉

edited VRM

After going into jumper mode and setting all jumpers like in a manual, in bios i don't even have a vcore option 😒 I can only see it in hardware monitor (2.0V), so i have no idea that my motherboard can handle tualatin/coppermine. BTW i have the same voltage chip as you.

Go into the BIOS
go to the screen Advanced Menu
highlight CPU Vcore
press enter
use + and - arrows on your keyboard to change voltage
exit BIOS and save changes

Well thats the main problem, i can't set voltage lower than 2,0V dosent matter if i use arrows or +/- it can't just let me set lower than 2,0V Here are the images:

- With jumper free config

- With jumpers set to 5,5 multiplier and 100 Mhz fsb

As I said before, those values will change will Coppermine/Tualatin CPU. You can also override them with proper Slot 1 adapter on something like Celeron Mendocino.

+this

Misha, you can can take a dive and plug in that Tualatin and hope for the best, or you can get yourself a cheap Coppermine Celeron like a 600Mhz with f.e 1.5 core voltage and see what happens when you start up.