How-to: Pencil mod your HD 3870!

[Random Murderer]

A few people have asked me how to perform this mod, and I'm kind of sick of finding the same things over and over, so I thought "What the hell? I'll write a tutorial!"

First things first:
I AM IN NO WAY RESPONSIBLE FOR ANY DAMAGE CAUSED BY READING THIS GUIDE, PERFORMING ANY ACTIONS MENTIONED WITHIN, OR FOR GENERAL STUPIDITY. NEITHER IS TECHPOWERUP.COM. YOU PERFORM ALL MODS AT YOUR OWN RISK.

Things you'll need:
1) A BRAIN AND THE ABILITY TO FOLLOW INSTRUCTIONS.
2) A digital multimeter(DMM) that can measure VDC and resistance.
3) A pencil, preferably 4H, but 4B works, and others have reported 2B working.
4) Adequate cooling for the voltage you choose.
5) A SOFT eraser. I used a "White Pearl" eraser.
6) A can of compressed air.
7) Either a printer or another computer, so you can view this while you're modding your card
8) Time and Patience.
9) A steady hand.
10) A set of... well, you get the idea

REFERENCE PICTURES:



Your default values may, and probably will, vary.
Second picture courtesy of FreakSavior.

Procedure:
Measure the 3D voltage of your card, make sure you are running a 3D intensive application, like the 3D window in ATiTool or the Fur Benchmark.
Do this by taking the negative lead of your DMM and grounding it to your computer chassis, and taking the positive lead of your DMM and touching it to one of the four measure points in the picture until the value displayed on your DMM stabilizes. Write this value down.
Shut down your system and remove your card. Test the resistance of R1222. The value should be around 1.5 KΩ. Write your value down. Grab your pencil and LIGHTLY shade resistor R1222. You may need to rough up the resistor slightly with a fine file. Blow off the excess pencil lead now and then and measure the resistance, for now we're shooting for .5 KΩ less than your default. Keep repeating the shading process until you reach this point.
Once you reach this point, the moment of truth arrives. Re-install your card, boot your system, and be sure to watch your temperatures as soon as Windows is booted. Run the fuzzy cube in ATiTool and re-test your VCore with the method from earlier and begin your overclocking!
If you don't have enough voltage, or you think you can push it further, you can always remove your card and continue shading to drop the resistance even more, just keep in mind that the temperature scaling is in no way linear to the amount of voltage, it is more exponential.

My Results:
Resistance stock: 1.5 KΩ
Voltage stock: 1.35 V under load
Core speed stock: 775 MHz
Resistance after mod: .933 KΩ
Voltage after mod: 1.44 V under load
Clock speed after mod: 891 MHz

Removal / Reversal of the Mod:
Just erase it! Make sure to erase lightly so as not to damage the resistor and test the resistance after erasing.

Things to Keep in Mind:
You'll need the fixed bios to reach speeds above 864MHz, so if you keep locking up here, it's not a lack of voltage.
This mod is easily reversed, and undetectable(once removed) if done correctly.
The temperature scaling is in no way linear to the amount of voltage.

BIOS Mods:
WARNING: Do not attempt to flash your card unless you know EXACTLY what you are doing.
I have put together and uploaded a .ZIP that contains ATIWinFlash 2.0.0.2, the PLL fix bios(named RV670 XT.BIN), and two overclocked BIOS files, one that runs 875/1250 and one that runs 860/1200, both named after their speeds(one is 8751250.sb, the other is 8601200.sb). Thanks to IAX-Tech for the modified BIOS files.
NOTE: These BIOS files DO NOT modify the voltages, just clock speeds, so it is still necessary to perform the volt mod.
I have also included a new .ZIP file that has a 38xx BIOS editing program. This does not work for the X2, so users of that beast should look elsewhere(sorry guys!).

This guide is a constant work-in-progress; if you have any questions or suggestions, don't hesitate to post them here or PM me.
Thanks to the guys over on XtremeSystems for putting their cards on the line to figure all this out.


BIOS editor

[a111087]

1st!
lol, nice tutorial, good pic and seems like this card will go very far with good cooling
EDIT: sticky?

[cdawall]

great guide rm

[Random Murderer]

Originally Posted by a111087

1st!
lol, nice tutorial, good pic and seems like this card will go very far with good cooling

Yep. One guy over on XS reached 1200 MHz using LN2.

Originally Posted by cdawall

great guide rm

Thanks.

[ShadowFold]

Will this work with a HD 3850?

[Random Murderer]

Originally Posted by ShadowFold

Will this work with a HD 3850?

Yep. Same resistor, different VCore measure point. I just don't have a 3850 on hand to make pictures of that though.

[reverze]

Thanks, can't wait to give it a go!

[ShadowFold]

So what does this do? Just make it faster? It wont destroy it right?

[Lazzer408]

How is it you guys figure out these mods? You have a source for schematics or something?

[Random Murderer]

Originally Posted by ShadowFold

So what does this do? Just make it faster? It wont destroy it right?

It depends on how much you lower the resistance and how well you cool the core.

[ShadowFold]

Originally Posted by Random Murderer

It depends on how much you lower the resistance and how well you cool the core.

I have the HIS IceQ i think I can adequatly cool it

[membreya]

Originally Posted by ShadowFold

So what does this do? Just make it faster? It wont destroy it right?

lower resistances, increase voltage..nah can't see it killing your card if you don't know what you're doing.

[Random Murderer]

Originally Posted by ShadowFold

I have the HIS IceQ i think I can adequatly cool it

You can always try it, just watch your temperatures closely!

[xt198]

holysh.... 891 core clock. i dont have ati, and i wont buy ati cards, but i see they are very capable to overclock :P
My question is:
if i overclock it from software (ex: to 800mhz core clock) and i make this pen-modding too, it will give more core clock, or the software is just activating in windows?

[tigger]

That should be fine.

[Random Murderer]

Originally Posted by ghost101

Can anyone suggest a better multimeter?

http://www.amazon.co.uk/Draper-60792...9271170&sr=8-1

I dont want to spend more than this.

That DMM has everything you need.
It's actually the same as mine, just different colors.

[trog100]

nice one random.. there is always a risk with this sort of stuff.. the bottom line is if u dont want to take the risk dont do it..

trog

[Solaris17]

Originally Posted by Lazzer408

How is it you guys figure out these mods? You have a source for schematics or something?

you can get design blueprints/schematics of the voltage regulation chips on the cards and the pcb layout..then you can just kinda figure it out from their because it gives you all the grounds resistances of certain resistors..and you just kinda put it together test it out then wright a guide.

stickied.

[DaMulta]

Originally Posted by xt198

holysh.... 891 core clock. i dont have ati, and i wont buy ati cards, but i see they are very capable to overclock :P
My question is:
if i overclock it from software (ex: to 800mhz core clock) and i make this pen-modding too, it will give more core clock, or the software is just activating in windows?

More voltage = able to clock it higher

[reverze]

...I want my VF900 now

[reverze]

Hmmm,

who sais...source?

I wanna read !

[sneekypeet]

hey Random WTF is the copper cooler on the card in the picture for?

[tigger]

extra cooling for the regs i guess,its on the other side of the board to them.

[sneekypeet]

I know but mine is never even the slightest warm to the touch....being an ex-1950PRO owner I checked it !

[Random Murderer]

Originally Posted by sneekypeet

hey Random WTF is the copper cooler on the card in the picture for?

Just an extra ramsink I had laying around, figured I would put it opposite the VRegs.