Sapphire HD5850 Xtreme / HD6850 Volt-Mods (vGPU & vMEM)

Sapphire HD5850 Xtreme / HD6850 Volt-Mods (vGPU & vMEM)



overview

The PCB is identical to those of HD6850s with AMD reference design. This means these mods can be used for HD6850 as well
A 4-phase switching regulator, which is located between the GPU and output panel, controls the GPU voltage. For the memory a simple single phase switching reg is beeing used.

http://www.abload.de/img/uebersichtxofd.jpg
*Spannung=voltage
*Last=load




voltage measurement

output caps of both switching regs are always a good spot for voltage readings. though the little MLCC at the back of VRAM ICs and GPU will give you a more accurate reading.

http://www.abload.de/img/messpunkte5trg.jpg


If u are using software like Trixx to adjust vGPU be aware that those values are different to the real voltage. Here's a table with exact measurement:

http://h3.abload.de/img/tabelleaiw8.png
*Spannung=voltage
*Last=load




vGPU mod

IC: CHiL 8214
FP Pin: Pin 4 (VSEN)
original resistance: 12.4 Ohms
recommended VR size: 500 Ohms

http://www.abload.de/img/vgpuyrdb.jpg
*Masse = ground
*put a 500 Ohm VR between FB Pin and GND




vMEM mod

IC: APW7165
FP Pin: Pin 6
original resistance: 5010 Ohms
recommended VR size: 200k Ohms

Pin 3 is a good ground spot. A pencil mod is possible alternatively

http://www.abload.de/img/vmem2t04.jpg

nice work, thanx for sharing

This mods work, but i have more problems whith OCP!!!:mad: Very low OCP limit, 1000mgz& 1,27v and GPU go on black screen. I try it on two diferent VGA (Sapp5850xtreme&Sapp6850). Need OCP-mod!!!!

That's very strange because I did torture tests at 1.35V and 1000MHz without such problems. On HD6850 it may be the weaker power supply which limits the power consumption to 150W.
The datasheet is not public so I can only speculate. There is definitely a per phase OCP. Changing the resistance at the corresponding 4 pins will likely change the OCP limit. But you can't be sure if it's either a increase or decrease. I guess you just have to try out.

http://www.abload.de/thumb/p1030888rdnw.jpg

Yes man, i tryed decrease this resistors whith pensil, but OCP limit stay alive. I try increase resistors soon and post here result.

Attachment 116473
Attachment 116474
May be i can playing whith marked red arrow resistors?

Quote:

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Originally Posted by mAlkAv!An

That's very strange because I did torture tests at 1.35V and 1000MHz without such problems. On HD6850 it may be the weaker power supply which limits the power consumption to 150W.
The datasheet is not public so I can only speculate. There is definitely a per phase OCP. Changing the resistance at the corresponding 4 pins will likely change the OCP limit. But you can't be sure if it's either a increase or decrease. I guess you just have to try out.

http://www.abload.de/thumb/p1030888rdnw.jpg

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Hi i need help with the XFX single vapo chamber fan 6850 it uses the APW7088 instead of the chil IC, i have the pinouts for the IC but the FB pin has no resistor across the soldier pins, ive tried trixx and afterburner the latest versions with all the relative stuff and EULA enabled and agreed but no voltage unlock is possible, have you any ideas ? many thnx in return