Saturday, July 12, 2008

Unleashing the 4850 Part 2 - Volt Modding

Now we're getting to the fun stuff. Volt modding is great way to get a cheap (free) jump in mhz. Often people are turned away by the thought of potentially damaging the gpu or reducing the life of the video card. In reality it is no different to overclocking and raising the vcore on a cpu. By raising the voltage in small increments and using the appropriate cooling, volt modding is perfectly safe and a great way to either truly push your video card to it's limits or just add some extra gaming performance.

You will need:
- Digital Multimeter. Do not perform any kind of volt mods without one of these.
- A low wattage soldering iron. A 15watt dick smith/jaycar cheapie will do the job. Make sure it has a nice sharp tip, otherwise it can get difficult in tight places.
- Some kind of wire cutters/strippers to make life a little easier.
- Small guage wire. Solid core is better for this stuff imho. I usually cut IDE cables into strips and use them. Perfect size for volt modding.
- A hot glue gun/double sided tape or alternative solution to mount components to pcb.
- Electrical tape (optional)
- 2 x 100k multiturn trimpots. Vertical or Horizontal. Used for adjusting voltage.
- 2 x 3pin fan headers - used for turning the mods on/off.
- 2 x jumpers from an old motherboard/hard drive. used with the 3pin header for on/off control.
- 1 x Molex connector for checking voltages

Now lets get started!

First up are the areas where the work needs to be done. Print these off before you take the video card out of your machine :).

This picture was borrowed from techpowerup. I didn't have a full shot of the rear yet.

VGPU - Solder 100k trimmer between this point and one of the grounds above.

VDDR - Solder a 100k trimpot between these two points.

Here's a picture of the VDDR mod completed. This enables you to raise the voltage to the RAM allowing extra memory speeds. Ramsinks are recommended when using this mod. I forgot to take pictures of the process but it is explained below in more detail for the VGPU mod.
I like to use regular 3pin fan headers combined with a standard motherboard jumper to turn the mod on/off. I have used this method for years and it's very effective if you do not want to run overclocked and overvoltage settings 24/7.

Click for Hi-Res version

Now we will move on to modding the GPU voltage (often reffered to as VGPU).
Here we are using a 100k trimpot. Either horizontal or vertical will work fine - i used vertical ones because that's what i had on hand :).
Here i have used double sided thermal tape to attach the trimmer to the pcb. I prefer using a small dab of hot glue but i wasn't able to locate the gun. I recommend cutting off the 3rd leg of the trimmer which is not required.

Click for Hi-Res version

Here is the trimmer attached to the pcb. Alway try to place it in a practical place which requires the least amount of wiring. Having them at the top edge of the pcb allows for easy adjustment and almost completely reduces the chance of shorting out components when rasing/lowering voltage.

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Like the VDDR mod, i like to use 3pin fan headers with jumpers to turn my mods on and off.

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I attached the fan header to the trimmer using more double sided tape. Again, i would recommend using a hot glue gun if you can stand the mess.
Here i have bent the middle pin of the trimmer up and soldered it to the middle pin of the fan header.

Click for Hi-Res version

Next we solder the pin from the fan header to ground. The other pin remains unused and you can remove it if you wish.

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Now attach a wire to the remaining leg of the trimmer ready to solder to the pcb. Remember to use heatshrink tubing over the connection to prevent any unwanted accidents.
Note: Don't use a lighter to shrink the tubing - cloth covered wire is quite flammable! I also managed to burn the wire. Poor form all-round.

Click for Hi-Res version

Lets solder the yellow wire to the pcb. Make sure you have a nice fine point on your soldering iron for this job, especially if you're new to soldering. The chisel point on my weller made it extremely difficult to do this. Remember - use the right tool for the job! Use some electrical tape as a bit of extra security to hold down the wire to the pcb to prevent it accidently catching on your finger while re-installing the cooler.

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Here's a picture of the VDDR and VGPU mods completed (and in the off position).
Hmm but how do we measure the voltage?

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Molex connectors are perfect for the job! Great size for a multimeter lead to sit safely inside. I used two test points on this one - one for VGPU and one for VDDR. It's generally a good idea to add another read point for GND, but it slipped my mind at the time.

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Here's a shot of the two read points. VDDR left and VGPU right.

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Here's a shot of all the mods completed.

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Next up i'll cover installing a waterblock and cooling the ram/mosfets.


reijin said...

Seems really simple - Would these be possible under air?

Because they're all the one GPU chip - The temps would stay pretty regular, I'd assume.

sandwichamwin said...

Yes it's safe to run under good air cooling. I would not add too much voltage though.

Just like a cpu, temps will raise as you add more voltage.