vmod basics [Archive] - XtremeSystems Forums

Ripper1

12-17-2002, 11:48 PM

ok, winter break is upon me and its time to vmod! i am very interested in it and want to learn but every post i see now just shows guides as how to vmod each part of the computer. i want to learn the basics and how it works and really get to have some fun with it. if possible, post some links so i can read up and learn and then try out some 9700 pro, nforce2 and amd vmodds ( i plan to have 9700 pro soon)...ok thanks

shortcircuit

01-01-2003, 04:40 AM

I was on vacation, I can reply in case you did not get this answered elsewhere.

You can start by finding the voltage regulator on whatever you want to mod. I did my first vold-mod on an old ACorp 7KT266A mobo (my first athlon board). On this board you can't adjust vcore.

I just looked around on the board and punched in the serial numbers of chips into yahoo. There was one chip, "ST L6917BD" which turned out to be the voltage regulator. My yahoo search led me to this link (http://www.st.com/stonline/books/pdf/docs/8162.pdf). It sure looked like the volgage regulator - it was DC/DC and had a range up to 1.85v.

Pins 18-21 determined the voltage. I found that I could very easily increase the voltage from 1.75v to 1.85v with one drop of solder. 1.75v was 00100 and 1.85v 00000, all I had to do was connect the middle pin to one next to it, and it would give me 1.85v. I tried it and it worked.

Normally though, when you're performing a voltmod you have already maxed out the normal capacity of the voltage regulator (in the case above, 1.85v). To go above this, you need to trick the regulator into thinking that the voltage is lower than it really is. You want to find a pin named VSEN or something similar to that. It should be a pin which monitors the output voltage and adjusts accordingly. You then need to connect that pin to ground using a resistor.

Most voltage regulators also have another circuit to see if you have exceeded a pre-set maximum voltage. This is known as OVP or Over Voltage Protection. To exceed the pre-set OVP voltage, you will need to do the same trick on this pin, connect it to ground with a resistor to drop down the voltage.

I'm not going to bother with mathematical formulas to determine which resistor you need for a given voltage. Sometimes you can get this info from the manufacturer's PDF file for the regulator. Just start small (BIG numbers like 1000kohms) and work your way up.

I would highly caution you to do your initial experimentations on a component that you do not care about. It's really easy to fry components doing this, and in the case of modding a mobo you have the possibility to fry other components like the cpu and ram at the same time.