ATI 3850/3870 Voltmod thread

[gigolo]

sure why not it's for 3850's 256Mb only be sure that you have 3850 with 256Mb Vram

use atiwinflash or atiflash to flash your card's bios

this one i'am using with one sapphire 3850 256Mb and i can go up to 1Ghz riva tuner cand go farther the card can go farther tho but we need a bios tuner with 38x0's support

Thank you again for this bios. I use powercolor 3850 256mb. I will try it with your bios.

[Vatos_locos]

@Norway what's the value (KΩ) on the mem Vr you used ?
can you gime me the magic trick for riva ati tool is not working for me it crashes all the time
Edit I found how to increase the slider now the question for the Vr is still remaining :p

gigolo no problem good luck

[eva2000]

anyone got a HD3850 pic of the volt mod and pencil mod locations... seems to be a bit confusing with HD3870 mixed in this thread

here's photo of my HIS HD3850 IceQ 3 card backside http://www.xtremesystems.org/forums/...d.php?t=171909

thanks

[Norway]

@Norway what's the value (KΩ) on the mem Vr you used ?

I Used a 500KΩ VR and the lowest volt i get is 1.9v, but I didn't measure it before the mod so maybe that is my default or i maybe just cant go so low as 1.86v that should be the default voltage .....

[Vatos_locos]

I Used a 500KΩ VR and the lowest volt i get is 1.9v, but I didn't measure it before the mod so maybe that is my default or i maybe just cant go so low as 1.86v that should be the default voltage .....

i think 1,9 is the default Vdimm for the 3850's with 256Mb so i guess you made the right choice anyway thanks again

[Vatos_locos]

@eva2000 try to measure point 1 and ground and see if it has 0 resistance then measure point 2 and 3 and see if the have 0 resistance iφ so the it should be the smd resistor between point 1--2 but you should wait for some one to tell you where the pencil point is for sure or try to lower this resistor 10-20 Ωhm and see if it raise your Vmem

[Riska]

Mine Sapphire 3870 can do 1331mhz on mem without vmod and stock voltage is 1.911v but when i do the vmod and set it to like 2.20v i cant go higher wy? how high voltage do you need for them mem on the 3870?

[Vatos_locos]

2,3Volt for every day should be fine but not more....
i don't know why you can't go higher but i thing that the memory frequency on those cards is already maxed out but i haven't try the mod yet so i can't really tel you why

[Riska]

When i set it to 2.31volt the thing articfats alot and crashes instant?

[Norway]

Vatos locos:
You talk about GDDR3 me and Riska talk about GDDR4 and 2.3v is ALOT (!!!) for GDDR4 .....

I wouldn't go any higher then 2.1v for everyday use under good cooling ....

I didn't do any thing special to hit 1400Mhz and that was on 1.95v, take of the mem HS and take a pic of one mem modul or just write down what is writen on it, also interesting to know what brand your card is Riska, mine is
Sapphire

Edit: i have done the OCP mod on both of my cards and they still lives
The resistors to replace is very small, i used size 0805 and they was a little to big so 0605 should fit just fine

[Riska]

Ok thanks norway i couldent understand wy it should be that high...

[Vatos_locos]

oh my bad i read 3850 sorry the yhea 2.0Volt are fine for 24/7 more for benchmarks only

[Menhir]

Vatos locos:
You talk about GDDR3 me and Riska talk about GDDR4 and 2.3v is ALOT (!!!) for GDDR4 .....

I wouldn't go any higher then 2.1v for everyday use under good cooling ....

I didn't do any thing special to hit 1400Mhz and that was on 1.95v, take of the mem HS and take a pic of one mem modul or just write down what is writen on it, also interesting to know what brand your card is Riska, mine is
Sapphire

is your card a 3870 with GDR4 memory or a 3850?

what voltage do u suggest for my 3850 512MB with Samsung 1.0ns ram

i've a vmod vor the GPU with 1.41Volt and can get GPU clock of 864Mhz
my ram is currently not vmodded and runs at 1035Mhz

my cooling is an accelero S1 with two 92x92 fans @ 12volt but without ram heatsinks because the ac heatsinks are crap

is it enough cooling when the fans blow direct onto the GDR?

[Norway]

You can pump up the volt, but wouldn't recommend you to nor run them without cooling 24/7 with more voltage.

On my 8800GTX (1ns memory) I used 2.24v to get 1215Mhz on the ram but I used swiftech ram sinks

I don't recommend swiftech becuase they always fall off

[akin]

@eva2000 try to measure point 1 and ground and see if it has 0 resistance then measure point 2 and 3 and see if the have 0 resistance iφ so the it should be the smd resistor between point 1--2 but you should wait for some one to tell you where the pencil point is for sure or try to lower this resistor 10-20 Ωhm and see if it raise your Vmem

also try to measure on the resistor located on the lower side..
in HD 3870 this Resistor is connect to FB pin (#2 left up ) to ground, so if you want to rise up the vMEM using pencil mod, just pencil this Resistor..

[eva2000]

@eva2000 try to measure point 1 and ground and see if it has 0 resistance then measure point 2 and 3 and see if the have 0 resistance iφ so the it should be the smd resistor between point 1--2 but you should wait for some one to tell you where the pencil point is for sure or try to lower this resistor 10-20 Ωhm and see if it raise your Vmem

thanks but I'm more looking for GPU mod.. as my memory can already do 1172mhz easy

[Menhir]

You can pump up the volt, but wouldn't recommend you to nor run them without cooling 24/7 with more voltage.

On my 8800GTX (1ns memory) I used 2.24v to get 1215Mhz on the ram but I used swiftech ram sinks

i was wondering because on my gecube 3850 turbo III the stock cooler doesent overlap one of the ram chips...

I don't recommend swiftech becuase they always fall off

that was my problem with this ac S1 heat sinks

[Riska]

Here is a good closeup of the vmem chip area.

[Norway]

i was wondering because on my gecube 3850 turbo III the stock cooler doesent overlap one of the ram chips...

Take a good (handfull ) bit of thermal grease and but on it and problem solved

[jimmyz]

thanks but I'm more looking for GPU mod.. as my memory can already do 1172mhz easy

Is this what you wanted? here is one of my modded cards, with v-core read point and a removable jumper for when I'm not benching.

[/IMG]

[the-strokes]

@ jimmyz / norway ; what's the resistance value (Ω) on the Vr to get 1.5v / above on VGPU ?

[Norway]

Haven't measured it, but whan it is soldered on you dont measured the value of the VR but on the whole cercuit that is around 5.05Kohm (?) default

[Riska]

Is there anyone ho has gained any Mhz on the Mem with Vmemmod??
No matter what voltage i set it to i cant get it any higher than with stock voltage!
Is there some other mod i have to do like in the old ati 9700-9800pro days there was 2 mods for the mem...

[Cha0s]

Hm doesnt it give a pencil-Vdimm mod?
Bios + Pencil Vgpumod is done and it rocks ^^
but now i wanna raise the Vmem...

[Riska]

http://www.xtremesystems.org/forums/...d.php?t=171996

Here it is