ATI 3850/3870 Voltmod thread

[Sagart]

I have now pencil mod'd the vcore so the circuit is a total off 4.59Kohm, default is it 5.1Kohm, what voltage should i expect vcore to be ?

I can calculate it if someone can give me a ohm value at a certain voltage

What's the stock voltage?

[HousERaT]

I have now pencil mod'd the vcore so the circuit is a total off 4.59Kohm, default is it 5.1Kohm, what voltage should i expect vcore to be ?

I can calculate it if someone can give me a ohm value at a certain voltage

Are you pencil modding a 3870? Where is the place that you used the pencil? Is it the same place as in post #159?

[Norway]

It is 1.33v but on my card it is 1.36v stock ......

[Norway]

I penciled the blue line


Or any other green spot to GND should work if i'm not completely screwed atm

[gurusan]

Wow thats great gurusan I have two of those cards and I'm waiting for good overclocking tool for cf. I will try the pencil mod when one comes out. what water block are you using?

MCW60

[HousERaT]

I penciled the blue line


Or any other green spot to GND should work if i'm not completely screwed atm

Simple enough....... now lets some some before and after results.

[Norway]

Be patient my young padawan

[HousERaT]

Be patient my young padawan

I'm waiting like a trick on a street corner.

[Norway]

strange, at 4.6Kohm I got stock volt, on 2.28Kohm i got the same result

[roger_h99.nor]

Consider yourself lucky. If, be chance, you've got the right spot to shade, you would have killed your card with that voltage.

Recommend some readup on the basics on v-modding.

[gurusan]

Is there a vdimm mod for the 3850?

[Norway]

Consider yourself lucky. If, be chance, you've got the right spot to shade, you would have killed your card with that voltage.

Recommend some readup on the basics on v-modding.

Well 4.6Kohm should give me around 1.5v, but it didnt happend so i tried half of it, also tried to shade the resistor but nope

Now i have taken som 470Kohm VR from school, but i am only to run stock air for now, water later so i wait for the solder work

TIP: Run your card on 50% fan 24/7, my max temp is 65C load on stock volt on 3870

[KainXS]

I just found out something unexpected, one of my 3850's has ram rated at DDR3 1000 and the other has it rated at 900, ATI could have easily overclocked these cards to have 1100 because the 8800GTS XXX uses slower DDR3 800 and can reach 1265, at least on my old one I could.

the voltage on both is 1.8V

Powercolor 3850 XTREME
Powercolor 3850 256

[Niccolò]

Well 4.6Kohm should give me around 1.5v, but it didnt happend so i tried half of it, also tried to shade the resistor but nope

Now i have taken som 470Kohm VR from school, but i am only to run stock air for now, water later so i wait for the solder work

TIP: Run your card on 50% fan 24/7, my max temp is 65C load on stock volt on 3870

Because that's the wrong spot.

I think i'm figuring it out, just wait a little bit and i'll post the resistor to shade.

[Niccolò]

Here it is



I had 0.1v increment by reducing it to 1.3 KOhm, so you can count if you want

Ps: obviously there's a K missing between 2.26 and Ohm

[KainXS]

and that will increase voltage?

[Clint]

Here it is



I had 0.1v increment by reducing it to 1.3 KOhm, so you can count if you want

Ps: obviously there's a K missing between 2.26 and Ohm

Hmm, my default HIS 3870 has a 1.62kOhm value there..

I did measure voltage and it is 1.34v, so there is something that doesn't add up.

[HousERaT]

I'm ready to start testing pencil mods as soon as someone demonstrates a working mod for the 3870.........

[RealyPssd]

Me too, hot damn.

[Niccolò]

I have a Sapphire 3850 512mb. For me it worked great... Dunno about your card, just try and you'll know it. But 99% i can bet it's the same mod for all cards (that has this pcb of course)

[HousERaT]

I have a Sapphire 3850 512mb. For me it worked great... Dunno about your card, just try and you'll know it. But 99% i can bet it's the same mod for all cards (that has this pcb of course)

so voltage went from what to what, and how much did it help your overclock?

[Niccolò]

I only raised it to 1.3v from 1.2v couse i'm on stock cooling.

Overclock went from 750 to 820.

I also tried a 1.35v an this is the result

http://www.pctunerup.com/up/image.ph...06864-954-.JPG

[Clint]

I shaded it down to 1.10kOhm from originally at 1.62kOhm.

Changes were:

1.62kOhm: 2D 1.24v and 3D 1.334v (891Mhz ATI Tool)

1.10kOhm: 2D 1.30v and 3D 1.40v (931Mhz ATI Tool)

(1.00kOhm: 2D 1.32v and 3D 1.415v) (945Mhz ATI Tool)


So it's confirmed working

EDIT: after some testing I can conclude that I have gained 40Mhz from raising 0.07 volt, wich I think is pretty darn good under a stock cooler
I now can run furry cube in ATI tool at 931Mhz, instead of 891Mhz.

Temps went up from 52C to 57C with stock cooler at 80%.

All in all a very sweet mod.

[Clint]

Finished a first bench in 3D06 @ 945/1250 without any hickups or artefacts.

Max load temp with stock fan at 100% was 54C.

EDIT: 1 hour of Crysis @ 945/1200 no problemo whatsoever, it actually seems like the stuttering and querkiness that I noticed before is gone...the voltage injection surely did wonders.
Max temp in Crysis was 57C, and I think thats the max I wanna do on stock heatsink.

Next step is to slap my modified 7900GTO cooler on there, 4 6mm heatpipes and some home made high flow ducting will allow 1.5 volt and 1Ghz on air...no question about it.

[Mayk-Freak]

my self modded HD3870 babies:


C2D@4180MHz & 2HD3870@ 1012MHz/1340MHz 3DMark06 19323 Punkte Vista64Bit