Radeon X800 Non-Pro/X800 XL/X850 Voltmods

Author: Urlyin
Date: 2005-02-11 12:48:55

Pencil Vmods & VID Vmods

We are seeing so many different variants of the ATI PCB from the OEM manufactures in regards to the layout of components, to the lack there of. For some this will be bad news, given the fact that there is no longer a SMR at R1597 on most PCI-E cards. This renders the pencil Vmod for the VCore unable to lower resistance to raise voltage enough to make a difference by just using the two solder pads to which the graphite will not stick. The reason for the not having the resistor can be best explained by ViperJohn.

by: ViperJohn
ATI didn't have to populate and create the voltage divider on the x850 PWA because they changed the VID jumper programming to increase 5240's programmed regulation setpoint from the gitgo.
Doing that they didn't have to trick the 5240 into regulating at a higher voltage by reducing the feedback voltage with a divider.
Which means we now have to use the VID vmod to change the VCore, but this is not adjustable. This however does not affect the use of a variable resistor as before and does not mean you still can not try the pencil on the VCore. Thanks to Kramda for reminding us of the Fan5240 VID settings.

With your card out of the system and your work area static free. Basically what we are trying to do is use our 2b pencil to reduce resistance on the selected resistor. You'll need to measure the resistance in Ohms first, by placing the black lead on one side and the red lead on the other side of the resistor, write it down it's our starting Ohm reading. Then gently run your pencil along the side of the resistor from one end to the other. Do a couple swipes then check again with the meter. Using the number you've written down subtract the new reading. For example, if your starting Ohm reading is .418k and your new reading is .400k obviously it's a 18k drop in resistance. If you go by the rule of 15k Ohms equals roughly .04V to .06V. Add the .04V - .06 V to the reading that you saved for future reference, for example the VCore reading of 1.39V your voltage should now be around 1.43V - 1.45V. A 10k variable resistor will give you around .04 Volts so again that's around 15k Ohms you need to reduce your resistor.
Keep in mind that if you want your card to last awhile don't get greedy.

VCore & IGPU Vmods

VCore & IGPU

Using the image above as our guide locate where the resistor R1597 used to be under the pencil labeled VGPU for those of you who still wish to try the Pencil Vmod. This is the two solder pads you will use the 2b pencil on, following the steps we went through above, but without a resistor, you'll try to use the space between or on either side of the pads to build a bridge.
Set your multimeter to 20k Ohms. A VCore voltage of 1.45V to 1.50V should work well. After you have reduced the resistance, place the card back in and power up. Check your VCore voltage again to verify the amount of voltage you're now running at. Test the card for artifacts and lockups. If all is well, use a piece of electrical tape and cover your work area. Review the max voltages suggested for cooling needs.

Now in most cases if not all, you'll need to do the VID Vmod to change VCore

The IGPU or Over Current Protection vmod is only needed, if you are applying a high VCore vmod. The higher the voltage your GPU runs at, the more power it consumes, the higher its current draw.
The VCore regulator chip has a built-in overcurrent protection feature which shuts the card down, if a certain amount of current draw is exceeded. This mod raises that limit.
In the above pic use a 20k Ohm reduction in resistance for OCP vmod, which is applied to resistor R1596. Since there isn't a measure point, remove the card and set your meter to 200k. Check the resistance on the resistor R1596 which should be around 40k Ohms. Lower the resistance by 20k Ohms.

VID Vmods

VID Vmod

VID Table

The VID Vmod requires a conductive pen or jumper to work. Looking at the image above, labeled VID Vmod, we can ascertain our default factory voltage by the placement of the SMR resistors by using the VID table below it. The picture shows a card with VID code 01101, which is 1.35V. By looking at the VID Vmod pic we can see, that there are SMD resistors at VID1, VID4 following the lines from pins 10 & 7 and by using the VID Table we use a zero(0) to show a resistor is present, with a 1 meaning no resistor present. So using 1.35V as an example to up the voltage using the VID setting we would use the VID table to determine a higher voltage with the same two SMR in place like the 1.55V setting to which we just connect the solder pads at VID2 with our conductive pen. Which would give a VID code of 01001. Unfortunately this limits our choices and for those with a 1.40V default voltage means the next available VID setting would be 1.60V without removing a SMR. Of course all is not lost if you are using a Water Block for cooling.

VDD & VDDQ Vmods

VDD Vmod

In above image locate the VDD labeled pencil above the resistor R311. This is the resistor you will use the 2b pencil on, following the steps we went through above. Set your multimeter to 20k Ohms. A 20k variable resistor which will give you around .08V Volts, you'll need to reduce the resistance around 30k Ohms. A VMem voltage of 2.08V to 2.12V will work fine. After you reduce the resistance, place the card back in and power up. Check your VMem voltage to verify the amount of voltage you are running your memory at. As we did in the VCore vmod, test the card for artifacts and lockups. Use the tape to keep the graphite in place. Review the max. voltages suggested for cooling needs.


This one will be a little tough given the resistor is in a tight spot. Again in the above pic locate the pencil labeled VDDQ above resistor R256, this is the one you'll need to pencil mod to increase VDDQ voltage. Set your meter to 2k Ohms this time. With the info of a 20k variable resistor giving .08 Volts we'll need to reduce resistance around 30 Ohms. A VDDQ voltage of 2.16V to 2.18V will help with both VCore and VMem. Check the voltage to verify the amount of voltage you're running at. Test for artifacts and lockups. Use the tape to keep the graphite in place. Review the max. voltages suggested for cooling needs.

 Variable Resistors »
Discuss this article in our forums