ATI 3850/3870 Voltmod thread

[Cha0s]

I did the old mod as well....penciling it was much easier, those solder points on new mod would just not connect for me...

I penciled it to like 1.249 ohms...Im not sure what vgpu that puts me at...

does anyone know of any measure points for voltage really close to the edge of the board on the side, cuz my vid card is very hard to measure since my cpu heatsink is so huge!...leaves me no room to put probes halfway in middle of card...

on the 3850 the measure point isnt in the middle it is here:

[GenTarkin]

sweet! and those are on the outer side of the board right? the side furthest away from motherboard?
Also what about those 2 beneath those points...are those just negatives and not positives like the ones you highlighted?

Or could I measure from those bottom 2 also?

[Jimbo Mahoney]

Does the 3870 have OVP or OCP like the 8800's?

If not, and all that is required to get high clocks is an unlocked BIOS and a vCore mod, I think I might save a few pennies and get a 3870 instead.

[Riska]

I dont think so i have had mine vgpu on 1.920volt on a mistake with no problem it can do a full 3dmark06 at 1.850volt and it is not getting hotter than 55c on my water

[Cha0s]

sweet! and those are on the outer side of the board right? the side furthest away from motherboard?
Also what about those 2 beneath those points...are those just negatives and not positives like the ones you highlighted?

Or could I measure from those bottom 2 also?

u should try it.. this picture isnt mine,.. i just copied it for showing you

[Cha0s]

Does the 3870 have OVP or OCP like the 8800's?

If not, and all that is required to get high clocks is an unlocked BIOS and a vCore mod, I think I might save a few pennies and get a 3870 instead.

OVP or OCP ? sry my english isnt as well...
german school-english

what do you mean? ,.

[Jimbo Mahoney]

OVP = over volt protection

OCP = over current protection

[JamesBong420]

sweet! and those are on the outer side of the board right? the side furthest away from motherboard?
Also what about those 2 beneath those points...are those just negatives and not positives like the ones you highlighted?

Or could I measure from those bottom 2 also?

thats my pic. its the ones close to the mobo. yes thats the positive side. it wont read correctly form negative. if you dont like that then you can read the volts from...

[Jimbo Mahoney]

Another question:

In the opening post, one image shows 100k for Vcore, the other shows 500k.

Which is correct / ideal? Is the second one a typo of 50k?

[largon]

It's not a typo.
But 100kΩ pot works much better than a 500kΩ one.

edit:
Here's a revised pic for alternative vGPU mod points:

[Vatos_locos]

one 100kΩ Vr is fine and easy tunable
500kΩ should be fine too but it will give you crap Voltage control

I have one question the mod's are the same for both cards ? 2850 and 3870 needs the same Vr's and we solder them at the same points ?
i'am waiting 2x3870 for Vmod :p

[KeZzZu]

Hi modded one of my 3870's powercolor pcs... and well gpu runs 3dmark06 with 1.48vgpu but mems cannot go over 1170mhz and mem default voltage is 1.98v :O should i try to raise or decrease? quite high voltage for gddr4 thought

btw hynix 0.8ns chips

[heanwi]

Could you post a picture of the mod KeZzZu? Got the same card so I'm interested in seeing how you did it

[KeZzZu]

Could you post a picture of the mod KeZzZu? Got the same card so I'm interested in seeing how you did it

sure in two hours. how fast your mems are going btw.. mine cant hit even 1200 mhz

[heanwi]

sure in two hours. how fast your mems are going btw.. mine cant hit even 1200 mhz

Currently at 1240MHz, but I have prioritized core clock so I haven't found a max mem clock (yet).

[Riska]

Here is my Sapphire HD3870 fully modded.

[KeZzZu]

Anyone else having issue to hit 1200mhz with 3870? mine has stock vmem 2v and mems are clearly overheating. 30 secs atitool and errors start to appearing, mems are hynix chips. cooling is crappy alu plate which i sanded clear and added thermal paste. gonna make good copper plate to cool them

ps: uploading mod pic asap

[Riska]

Mine is 1.897v stock and hits 1331 fully playble for hours but cn do 1377 bench

[KeZzZu]

Mine is 1.897v stock and hits 1331 fully playble for hours but cn do 1377 bench

hmm maybe powercolor using some bad chips on their cards, should i try vmem mod and whats max 24/7 vmem ?

[TI66ER]

Thats really nice tidy work there riska.

[KeZzZu]

here is powercolor pcs model vgpu mod. Caution i dont take any responcebilities about cracked hardware! shade with caution! measure before use and be sure it's same component lay out! works for me. that component is shaded as you can see ^^


http://xs123.xs.to/xs123/08020/picture_008622.jpg

[Riska]

Thanks man i hate messy vmods

[Jimbo Mahoney]

Is it fair to say that the memory doesn't benefit from more voltage?

That seems to be the case from reading this thread...

[TI66ER]

If i connect my 100kohm trimmer from the yellow point to ground,is that correct? Also what do i need to set the resistance to on the pot,before i boot up? My pot is a 100kohm cermet 22 turn

Thank you guys



This is not my card which is a his3850 256mb,but the mod is the same for the 3850/70 is it not? apart from the vgpu measure points.

I just want to make sure i do this right.

EDIT-just measured vgpu while 3dmark06 was running,its hovering around 1.23-1.24v

I just put my trimmer on.It is set on max resitance and the vgpu as it booted was 1.24vgpu.So now i just need to lower the resistance on the pot a tad and see if it goes up on 3dmark06 from 1.24v.

[TI66ER]

well i set the vgpu to 1.36vgpu and tried it at 790mhz core on 3d06.It stomped it,this is with the core at 790mhz and my ram stock.It beat my stock score by loads.

It seems the 22turn trimmer i have is roughly equal to 0.1volt increase per 3 full turns of the screw.

The max temp while running 3d06 with the voltage on 1.36v was 53c using riva tuner to monitor it while i ran 3dmark.



My old stock score with core and ram stock was 9800