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Hi, every one, here I found the galaxy GTS250 uses a RT8841 power supply chip. I also found the pin configurations for RT8841 (FB is pin #6). The stock vGPU is 1.2V, the board also have a jumper to set the vGPU to 1.3V(maybe). Can anyone sketch a wire/resistor connection to do the vmod down to 1.1/1.15V? Thanks!
http://i106.photobucket.com/albums/m...o/RT8841_1.jpg
http://i106.photobucket.com/albums/m...o/RT8841_2.jpg
more pics on the PCB, top view, back view
http://i106.photobucket.com/albums/m...photo/gts3.jpg
http://i106.photobucket.com/albums/m...photo/gts4.jpg
Thats easy enough. VID is controlled by pins 33-> 40. If you pull up the datasheet it will give you a list of VID options based on which pins ar held low or...not.
Dont have time to really go through it right now...sorry!
This jumper interests me, if we can do mods on the jumper, it would be easier
The default jumper state is in the right pin and the middle pin (1.2V and GND)
Look at the two resistors in the red circle, if the voltage is controlled by the two resistors, changing the resistance value may achieve the vmod. I will measure the resistance value of the two resistors later.
however, if I remove the jumper and boot the system, the GPU temperature changes from 58C to 64C, so vGPU may increase after removing the jumper.
http://i106.photobucket.com/albums/m...oto/gts4_2.jpg
new working results, with the measuring value of the voltage meter:
jumper 0,1 1.23v idle/ 1.25v load 807MHz max
jumper 1,2 1.28v idle/ 1.30v load 824MHz max
remove the jumper 1.18v idle, 1.19v load 785Mhz max