ATI 4850/4870 voltmod thread

[Krautmaster]

does anybody have the problem that 3 to 5 trys are needed to boot a system with an OC HD4850?

When my sytem was off for a few hours, i can turn it on but screen stays black. Can do this several times. Sometimes i need to disconnect PSU and connect it again. Board is an P5K-E with 480 FSB. PSU has 1200 W Silverstone, 28A on 12V per rail.
Tried some newer P5K-E bios versions, nothing helped. Any ideas?

[Utnorris]

So I have a couple quick questions before attempting this mod after reading virtually the whole thread. I just want to be clear on what I need to do:

This will be for a Visiontek 4850 under water cooling. Current temps are 32c idle and 37c load with ambient of 25-27c.

1 - Theta stated earlier that if you want a specific voltage you could use a fixed resistor:

10 ohm fixed ~ 1.566v
15 ohm fixed ~ 1.465v
22 ohm fixed ~ 1.400v
27 ohm fixed ~ 1.375v
33 ohm fixed ~ 1.355v

Does this still hold true?

2 - Where do you measure the voltage to see if it worked or not? On the card while it is turned on? In windows? Can you just connect a 12v PSU to it and power it on to see the voltage without having it installed on a MB?

3- Where am I measuring resistance at, between the two solder points?

4 - I grabbed this pic from earlier in the thread showing where to solder for both GPU and Mem voltages. Is it correct?


By utnorris at 2008-11-08

[roger_h99.nor]

Voltmod http://www.powercolor.com/Global/pro...ProductID=2355 confirmed working. 10 Ohm fixed and a 50 Ohm in series.

This card is benchable around 880 gpu w/o mod. Expect at least 950 after mod. Testing about to commence

[trez0r]

I have an Asus EAH 4870 512mb non-reference card.



My thoughts about it can be read in this post. The card does really weak on the core overclocking. Perhaps i might do a mod and see if that helps. Unfortunately i don't seem to find any info on voltmodding this card. Any help would be appreciated.

Thanks!

[NapalmV5]

Voltmod http://www.powercolor.com/Global/pro...ProductID=2355 confirmed working. 10 Ohm fixed and a 50 Ohm in series.

This card is benchable around 880 gpu w/o mod. Expect at least 950 after mod. Testing about to commence

nice..

can you confirm the 3x 47uf poscap on your 4870

http://www.edc.sanyo.com/english/pdf/poscap/E42.pdf

thanks

[Vatos_locos]

trez0r some hight res. pic's of the card would be helpful

[roger_h99.nor]

nice..

can you confirm the 3x 47uf poscap on your 4870

http://www.edc.sanyo.com/english/pdf/poscap/E42.pdf

thanks

Hi, can not recall to have seen caps similar to those in the pdf, but if you could suggest where to look for them, I'll sure have a closer peek.

[NBF]

try an other Bios

Tried 5 different BIOSes, none worked

I guess ill need one from a Powercolor/Club3D 4850 with DVI-HDMI-DisplayPort, which I couldnt find.

I would be tankfull if somebody that have one of this cards could upload a copy.

[kur¡]

Hi friends. I received my 4870 sapphire from rma.... but... this 4870 have blue pcb and i would like to do a vmod. Someone know if the vmod is the same , like 4870 with red pcb?

[ceemic]

kur¡, is the layout same? Same IC?

[Duniek]

NBF, I talked with my friend Jaan (some of here might know him for his exteme Vmoding skills) atm. He gave some hints how to look right place. I'll do some measurements and report back. And it can be the BD-AF IC

EDIT: I tried to figure something and here are my thoughts:
http://ceemic.pri.ee/hardware/hd4850_2/hd4850_02g.JPG
First bet would be "14" marked on my pic. Resistance to GND is ~1002 ohm (~1,0k ohm). If You have time maybe You can confirm it? 20k VR should be safe. There are many good soldering points. Sadly, I don't have time to try it next 2 days...

my friend has the same card as you

How can he make pencil-mod for vcore ??
thanks in advance

[ceemic]

Duniek, I'm not that confident on pencil moding. I don't like pencil mods, because they are not that reliable and it's bigger possibility to kill the card. I don't see there any SMD resistor that could be pencil-moded. The only point where GND is other spot:

[NBF]

Duniek, I'm not that confident on pencil moding. I don't like pencil mods, because they are not that reliable and it's bigger possibility to kill the card. I don't see there any SMD resistor that could be pencil-moded. The only point where GND is other spot:

I have done on that exact spot, I did it for a friend that didn't want soldering on the card.

It works fine, just have to be very carefull with the pencil.

Lowering #14 -> gnd resistance to ~950ohm give around 1.4V on the GPU.

[ceemic]

NBF, tnx! Yep, it should work. It's vital to measure resistance drop after every pencil stripe...

[Duniek]

Duniek, I'm not that confident on pencil moding. I don't like pencil mods, because they are not that reliable and it's bigger possibility to kill the card. I don't see there any SMD resistor that could be pencil-moded. The only point where GND is other spot:
http://ceemic.pri.ee/hardware/hd4850...50_mod_pen.JPG

thank you
it works, but one more question I hope last
where he can measure vcore on gpu, I mean which point or points I should check?

[ceemic]

Duniek, http://ceemic.pri.ee/hardware/hd4850..._mod01_mon.jpg

[Jimbo Mahoney]

Will the 4830 mod in the same way as the 4850 do you think?

I'm thinking of saving a few £££ and going for a 4830 and using good old modding and overclocking to get more bang out of it.

Hopefully not the bad, electrical, flashy kind of bang though

[ceemic]

Jimbo Mahoney, You have to know what PWM controller there is. Do some macro close-up's from IC and PWM.

[Barr3l Rid3r]

Asus EAH4850/HTDI/512M has 3 phases.
Both EAH4850/TOP/HTDI/512M and EAH4850/HTDI/1G have just 2 phases, not 4 (inductors ≠ phases).

What did you ask from Diamond? To help with a vmod?

But u told that 4850Ics can handle only up to 2 phases? What about Gigabyte Blue UD and Gainward GS 4850? Both looks like an 4+1 design...

[ceemic]

Barr3l Rid3r,they have other ICs which can operate with more phases?

[8800's@over]

How do I explain why I get black screen with the Core over 835MHz?

[Vatos_locos]

locked bios maybe ? try one from the Internet

[ceemic]

8800's@over, save the BIOS with GPU-Z and then open it with newer RBE. So You'll see the max limit and can edit it too...

[DJSUB]

anyone with oc'ed 4850 800+mhz core 1150+mhz mems that works on newer catalyst driver?

i can't get my 4850 870/1200 to work on newer catalyst. it only works with catalyst 8.7
any tips to make it work on a newer driver?

thanks in advance

[ceemic]

DJSUB, same problem here with 4850 and 4870. The problem occurs when I change max clock limits with RBE...