ATI 3850/3870 Voltmod thread

[gurusan]

Well it's really a subjective thing, some people are comfortable running 1.7v through their C2D chips...and TBH I have not heard of too many people actually frying them.

However, I would be pretty nervous running 1.65v through a 38xx GPU 24/7 even with watercooling. I'd be comfortable with 1.5-1.525 daily.

[spookywillow]

yeah i probably will drop it as the other components look pretty cheap but for now its fun testing, trying for the magic 1ghz but i just tried and it aint happening without more voltage lol

[xixou]

I don't need it anymore, I got i from the manufacturer.

[Jimbo Mahoney]

ok i sorted the OCP on my card, i dont know what the max voltage i can run but its running 1.65 (1.63 under load) had to put the water block back on as temps shot to 90c instantly with the stock cooler but they are around 55c now on water.

to get past OCP with a pencil mod i shaded a few resistors, the 2 marked in the blue box and the one to the right of the smaller blue box.



R657 initial resistance 6 ohms - lowered to 4.3 ohms
R659 initial resistance 6 ohms - lowered to 4.3 ohms

R658 initial resistance 100 ohms - lowered to 46 ohms

off to do some testing

Hi Spooky,

It's awesome you've managed to get round the OCP. I've been stuck at 1.53 on my Triplex 3850 (uses the same Nexsem 2415).

Do you need to pencil all three of the resistors you mention?

Couldyou explain your reasoning behind them? I tried to get my head around the datasheet and my assumption was increasing the resistance of R658 would defeat OCP. I removed that resistor, since that was easier than soldering a VR (I don't trust pencil...) but the OCP remained.

Many thanks for your help!

[spookywillow]

thanks

i just looked at a few other mods and looked for what pins are being connected and looked for the same type of thing on my card after looking at your pic,

i couldn't understand the calculations on the data sheet tbh, i just saw what pins i needed to look for and traced them on the pcb. i shaded all 3 a little to get started and it worked.

i have since found that R657 and R659 are directly connected so shading either one will do the same as shading both. R658 does not need shading at all.

i think R658 is just used to select the OCP detection type as it says something about that in the pdf, its actually PGSEN that needs to be changed

[MagnumMan]

I just wanted to post some thanks to everyone here who provided all the pictures and knowledge on doing these mods. I hardmodded a 3870 with trimmers for GPU and Memory voltage (to 1.6V and 2.05V respectively) and got a stable card running at 940/1210 using the stock cooler, it doesn't exceed 80 degrees C under load but I figure I pushed it enough. I was able to bench it at 1280 memory with some artifacts and 1210 without. While I was at it, I replaced many of the 180uf caps with 330uf, and added more 220uf caps in the spots where there were none. On the 2.5V plane I added 1x 2200uf cap to the top of the board (memory) and 2x 2200uf behind the board, so the board's capacitance increased about three-fold.

One thing I found was that my Weller WD1000M goes up to a max temperature of 850 degrees F. I found this was not sufficient to melt the solder used on the board (as I wanted to remove the 800uf caps, but I could not melt the solder!) so I had to just tack on a couple loose ones and glue them down.

I have 4 more water cooled cards I want to modify the same way, as I can push the voltage way up on those. I just learned from MSI Tech Support that they will NOT be adding a Northbridge multiplier into the K9A2 Platinum (V1) BIOS. They used to have it in a beta bios (1.13). They claim due to lack of hardware support which is complete crap. So I will be looking for another motherboard for my water cooled beast.

[Random Murderer]

I just wanted to post some thanks to everyone here who provided all the pictures and knowledge on doing these mods. I hardmodded a 3870 with trimmers for GPU and Memory voltage (to 1.6V and 2.05V respectively) and got a stable card running at 940/1210 using the stock cooler, it doesn't exceed 80 degrees C under load but I figure I pushed it enough. I was able to bench it at 1280 memory with some artifacts and 1210 without. While I was at it, I replaced many of the 180uf caps with 330uf, and added more 220uf caps in the spots where there were none. On the 2.5V plane I added 1x 2200uf cap to the top of the board (memory) and 2x 2200uf behind the board, so the board's capacitance increased about three-fold.

One thing I found was that my Weller WD1000M goes up to a max temperature of 850 degrees F. I found this was not sufficient to melt the solder used on the board (as I wanted to remove the 800uf caps, but I could not melt the solder!) so I had to just tack on a couple loose ones and glue them down.

I have 4 more water cooled cards I want to modify the same way, as I can push the voltage way up on those. I just learned from MSI Tech Support that they will NOT be adding a Northbridge multiplier into the K9A2 Platinum (V1) BIOS. They used to have it in a beta bios (1.13). They claim due to lack of hardware support which is complete crap. So I will be looking for another motherboard for my water cooled beast.

850°F should be fine. try using a dab of flux on the joint to help reflow the solder.

Also, i noticed that the VMem mod only caused artifacts on my cards even at stock clocks. the .8 ns memory on these cards should be good for 1250MHz even at stock voltage. if you can't reach that, try removing the mod.

[spookywillow]

can i ask how it helps to put more capacitors on the board? i saw that in shams pic of this mod and wondered why he did it.

also what is default voltage for the ram? my card uses a different design and the only thing i can find that remotely looks like the VMem mod pic is an IC called nexsem 2114 http://www.nexsem.com/pdfs/2114DS.pdf i assume thats the IC i need but theres only 3 capacitors near it and 1 reads 2.08v and the other 2 read 1.64v.

my gpu was undervolted to begin with and wouldn't run at stock clocks and my ram wont run at anything past 1150 so i'm assuming again that the 1.64v is my Vdimm :/

random i'll send you a pm at tpu now if your about m8

[gurusan]

Does anyone have the single slot sapphire 3870? Is it more or less the same? I'll be getting one to crossfire with my 3850 and am hoping vmodding it will be as easy as with my powercolor 3850.

This one:

[Eldonko]

Very nice MagnumMan, could you post a pic or 2?

[xixou]

I have overclocked my hd3850 AGP Powercolor.
11572 points 3dmark06 (1280*1024).

(1.39 volt instead of 1.33) to push till 891 Mhz (GPU) and 1017 Mhz (MEM).

[OnDborder]

Anyone have a pic of measuring points for the "blue/old" 3870 pencil mod?
I can't get the yellow to work..

[blind_ripper]

Put them here so largon can tell you the next step. So our cards have the same power regulator chip and the same layout?

Thanks for doing it anyway

Pin#7 on the smaller chip (AT-9J?) = 5.46k ohms
Pin#13 on the larger chip (BD-9J?) = 5.92k omhs

can some1 now find me the mod ?

[STaRGaZeR]

Nice, now we need that mod

[gurusan]

Hey everyone, I just got an older blue single slot sapphire card. It's a bit different to my powercolor 3850. Can anyone tell me which resistor I need to shade?

(excuse the dust :p )

[Mayk-Freak]

Mayk-Freak:

Can you post your BIOS settings ?

Sorry for the late answer. But I´m sorry, I don´t have the board anymore.

[STaRGaZeR]

Pin#7 on the smaller chip (AT-9J?) = 5.46k ohms
Pin#13 on the larger chip (BD-9J?) = 5.92k omhs

can some1 now find me the mod ?

Any news? largon?

My new card should be here in a few days, will test it if it's already done

[blind_ripper]

finding mods with team member geoffrey , also check bios ver plz ! i have 010.73v if some1 can mod it to kill the bouncer ? cant flash any other on it , some date is wrong .

[STaRGaZeR]

My card came with BIOS 010.078, and didn't have any lock at 862MHz. Do you want it?

Oh and hope you find the mod soon

[blind_ripper]

these are the points that read-out 0 ohms with vgpu read-out as ground so within those points we have vgpu mod .

think mine has lock so thats why i needed a unlocked ,
yes send it in a pm if u want thx

[G.Foyle]

gurusan, shade the circled one:


On my one card resistance measured on that resistor was around 2.2 kΩ, with stock voltage 1.222V lowering resistance to 1.3kΩ resulted in 1.267V
on the other card resistance was 1.7kΩ, lowering to 1.3kΩ gave me 1.302V.

[gurusan]

thanks so much xoqolatl

[G.Foyle]

I had to put an awful lot of 6B pencil on that resistor to get to 1.3kΩ. When your done with tuning your resistance, you can secure the mod in place with a big drop of nail polish (seriously).

[chp]

Seems to be true when using stock volts...but once you vmod them they seem to clock roughly the same....my powercolor 3850 does 1012mhz @ 1.55v, 960mhz @ 1.5

Hi gurusan,

I think have the same Powercolor as you (I think it's the HD3850 PCS-512) and I've done the VMOD but I can't pass the 823MHz stable @ 1,47V without black sceens durring 3D tests after 1 to 5 mn (sometimes immediately)

I tried also 864MHz @ 1,52 with no luck

So, I have some noob questions (hope you'll help me):

1) where, when and how do you test your volts. I mean I use a MM to test between the points shown in the pictures but I don't know if I need to be running a 3D app to test or not.

2) What bios do you use? For my part, I tried many and the one wich shows the best performance in 3DM06 is the HIS HD3850 IceCube one (xxx.O77.xxx).

I removed the original Powercolor cripled cooler and put an original ZeroTherm 810 wich allows the fan to rise the rpm depending of the heat.Now, my temps aree fine in load (atitool's artefact scan) with max 65 - 67 degres @ 1,47V for 823MHz.

[G.Foyle]

1) where, when and how do you test your volts. I mean I use a MM to test between the points shown in the pictures but I don't know if I need to be running a 3D app to test or not.

measure point is here (dont mind the PCB color):

Voltage at boot is different than when running 3D app; run 3DMark or ATI Tool artifact tester then measure.