pencil moding 4850

[Albyno]

ok ive read thru all the reviews/rightups/how toos for this mod but am still not 100% confident on what i actualy need to draw over for this mod.

my understanding is that you use a grafite pencil (2h or something is the 'best') and draw over a resistor (or other chip) to trick it into thinking it is delivering less power then it actualy is and therefor it will increase its duty cycle and thus the volts delivered.

if anyone has done this mod on a 4850 would you mind posting a few pics of the before (i you have) and the after pics. at least after as i have my own 4850 to compair with. i read the article on another site which shows the pencil and its tip on a lil resistor (i think thats what it is) but no actual lines on it.... or because its grafite is that the result?

and finaly if i do go ahead with this do you use a DMM to find out what volts it is putting out? or is there software that will tell me

All help on this will be soooooo much apreciated

Tim

[jason4207]

ok ive read thru all the reviews/rightups/how toos for this mod but am still not 100% confident on what i actualy need to draw over for this mod.

my understanding is that you use a grafite pencil (2h or something is the 'best') and draw over a resistor (or other chip) to trick it into thinking it is delivering less power then it actualy is and therefor it will increase its duty cycle and thus the volts delivered.

if anyone has done this mod on a 4850 would you mind posting a few pics of the before (i you have) and the after pics. at least after as i have my own 4850 to compair with. i read the article on another site which shows the pencil and its tip on a lil resistor (i think thats what it is) but no actual lines on it.... or because its grafite is that the result?

and finaly if i do go ahead with this do you use a DMM to find out what volts it is putting out? or is there software that will tell me

All help on this will be soooooo much apreciated

Tim

Read this first! (http://www.ocforums.com/showthread.php?t=568166)

Read this as well. (http://www.xtremesystems.org/forums/showthread.php?t=190990)

You're going to need a DMM before you do anything. You're going to want to measure the resistance before and after you pencil. You'll be drawing across a SMR (surface mount resistor) or the PCB itself to reduce resistance and increase voltage. I use a quick burst of canned air to blow off extra graphite particles b/n measurements.

1. Take initial Ohm measurements.

2. Use pencil.

3. Blow off excess.

4. Take more Ohm measurements to see where you've gotten.

5. Use pencil or eraser to re-adjust.

6. Boot PC, and take voltage measurements to confirm. Make sure to run ATI Tool or similar to put card into 3D mode, so you can see 3D load voltages.

IMO it is pretty hard to get it just where you want it. It took me several hours, and I still wasn't satisfied (I might be spoiled by solder-type mods, though).

[Albyno]

so i NEED to take a measurement of the card both with and without power?

i have a DMM thats no probs. after i pencil i want the measurement to increase correct? say 0.4-0.8?

[jason4207]

so i NEED to take a measurement of the card both with and without power?

i have a DMM thats no probs. after i pencil i want the measurement to increase correct? say 0.4-0.8?

Yes, you want to use resistance measurements while the card is on your work bench to predict where the voltage will end up and prevent you from giving the card too much juice. The links I provided give you a few Ohm values and their corresponding voltages.

The more graphite you add the lower the resistance will be, and the higher the corresponding voltage will be. You're basically adding a resistor in parallel. You're giving the circuit a new path to ground. If that path is too wide (resistance is too low) then you'll get very high voltages. If you soldered a wire across there you'd have 0 Ohms, and a short circuit (voltage would increase exponentially until it fried).

You may have to do a little experimenting also. If you put the card in, and get 1.2v+ while in 2D mode you might want to take the card back out and try removing some graphite before going into 3D mode.

Also, the TechPowerUp instructions have 2 places to pencil for the vGPU mod. I haven't seen anyone post the Ohm values and their corresponding voltages for the SMR location which, according to the article, is the best place to start. I just penciled across the 2nd location (across the PCB), and it worked, but it was frustrating getting the vGPU dialed in just where I wanted it.

I was getting 5.09k Ohms (1.15v under load) between the 2 PCB pencil points before modding. I penciled down to 4.98k Ohms, and got 1.218v under load. 4.92k Ohms netted me 1.233v under load.

It might be better to try the SMR first, but I don't know the Ohm values to shoot for across the SMR.

[Albyno]

ok im pretty confident on what to do now once again thanks Jason your help is ALLWAYS useful, might try it on my 7600 first not sure may go for the 4850 strait out. just lastly that 1.233v you measure was whilst the card was in the PC running right? so i really cant do this without testing it running with a DMM no software can tell me

[jason4207]

ok im pretty confident on what to do now once again thanks Jason your help is ALLWAYS useful, might try it on my 7600 first not sure may go for the 4850 strait out. just lastly that 1.233v you measure was whilst the card was in the PC running right? so i really cant do this without testing it running with a DMM no software can tell me

Yes, you measure resistance w/ the card out of the PC. This will let you know if your in the ballpark.

Then put the card in the PC, and boot up (w/ fingers crossed!). Once your at the desktop, start measuring voltages. Load up a 3D app, and measure voltages again.

[MadMan007]

I figure that it would be worth a mention here that you can get up to 1.2V real by setting 1.263V or higher with a BIOS mod and flash.

[Albyno]

ok tonight it is then. last question which setting on my DMM do i wanna use for ohm/resistance measurements?

[jason4207]

20k

[Albyno]

k gave it a shot the mem one went down no problems but couldnt get the GPU one to move. it did at one stage drop.02 then went up point .02 over what i started on :S

any ideas why that would happen?

[Albyno]

*edit found my answer for this post not the one above

[jason4207]

k gave it a shot the mem one went down no problems but couldnt get the GPU one to move. it did at one stage drop.02 then went up point .02 over what i started on :S

any ideas why that would happen?

You're reading the resistance, right? So, that's 0.02k Ohms. Can you post a pic of your measuring spots, and where you're penciling?

When I did it I was getting weird results until I penciled the 2nd spot recommended in the TechPowerUp article....the spot across the PCB. At first I was measuring the resistance b/n the 2 solder blobs at the PCB location, and penciling the SMR. I saw no change in resistance. Then I penciled across the PCB, and saw a lot of difference. I had 4.68k Ohms on the DMM, and tried it out...1.5v+ under load! I killed it quick, and started over making sure to fully erase the pencil marks over the SMR. I think the SMR location was affecting my voltage, but I wasn't measuring it correctly.

I then worked exclusively on the PCB spot. I retrospect I think I should have measured across the SMR while penciling across it, but there is no documentation online (that I've seen) as to a good goal to shoot for when measuring across it. The PCB spot is better documented, and after several tries w/ the pencil and eraser I got it in a good spot for the stock cooler.

The penciling did frustrate me. Now I'm using hard-mods, and it is lovely!

:beer:

[Albyno]

hmm might try the PCB spot then. when measuring the PCB resistance do you put both prongs on the two solder spots where you will be penciling? or one there and one on the earth?

im 99% sure i was measuing the first spot right (the SMR) becuase when i went onto the ram SMR it worked properly.

[jason4207]

hmm might try the PCB spot then. when measuring the PCB resistance do you put both prongs on the two solder spots where you will be penciling? or one there and one on the earth?

im 99% sure i was measuing the first spot right (the SMR) becuase when i went onto the ram SMR it worked properly.

Yes, the 2 solder points you're penciling b/n is the correct spot to measure. One of them might even be ground, but I'm not certain on that.

You should get close to 5.09k Ohms before penciling. If you decide to go the PCB route then make sure to erase the pencil marks on the SMR location.

Edit: A note on the mem mod. I was getting black screens until I switched coolers, and sinked everything in site on the board.

http://img364.imageshack.us/img364/1851/p8020071gs6.jpg

http://img359.imageshack.us/img359/2145/p8020072dw9.jpg

http://img363.imageshack.us/img363/7334/p8020073bh4.jpg

[Albyno]

ok so done again is it posible that too much volts would cause that card to make 'strange' sounds..... i cant pin point where the sound is coming from but it happens when in 3d mode 2d is fine.

clocks upto 700/1075 atm tho for a 13500 3d06 score

[Albyno]

also what is holding ur swiftech sinks on jason? the stuff they come with on them is total crap almost all have fallen off now for no reason. there i am sitting on my chair and plop sink falls off. 15 mins later a dif one falls off

[flopper]

clean ram area with good solvent.
some even glue the sinks to the board in a small corner of the ram.

[jason4207]

I used goo-gone, and 91% rubbing alcohol to clean them. I've learned from past experience that even if they look clean you need to take an extra step to get the 'greasy' layer off.

You may need to get some new tape if you try to re-apply them. I went through that process on my 8800GTS. Once they come off the tape tends to absorb some of the 'grease', and they never stick again. Luckily, I have some good thermal tape here.

[Albyno]

any idea what the kinda buzzing/squeeking sound is when the card ramps up to 3d mode/full clock?

i cant figure it out but it even does it scrolling web pages. but not movies

[Albyno]

tested the volts running now thanks to me gf holding the DMM whilst i put the prongs on.

got 1.23 core atm... with the first core voltage mod 1.23 was enough to make it 700 stable
2.03 mem atm....with the mem mod is enough for 1075 atm will shoot for higher mem later in the week but from what ive seen core seems to improve benchmark scores more then mem speeds.