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Voltage mod/GpuV read on POV 9800 gt Help request

post #1 of 9
Thread Starter 
Hi Overclock.net

i have been lurking on this for quite some time now and it has inspired me to do my own voltage mod on my point of view 9800 gt.

i checked the essentials of vmod'ing post that cl3p20 and pizzaman has contributed to. Even though i spent a lot of time reading through all the pages (thats like 60 or so) i still need some help biggrin.gif

i located the voltage regulator on the gfx and it seems to be a RT8802A. I read the datasheet and according to the datasheet pin 4 on the chip is the feedback pin.

IC_rt8802a_big_thumb.jpg

i used my DMM to check if there was continuity between the pin i located as pin 4 and the resistor. Afterwards i used my DMM to measure the resistor between the redspot on the resistor and ground/0V which gave me a reading of 5.6K ohms. I believe a 100-120K VR would do the job for my voltage mod, can anyone confirm?

IMG_3609_big_thumb.JPG

also could anyone tell me where the correct point for measuring gpuV? i've tried some different spots, but i i got multiple results all though within the range of 1.105 to 1.115 which one.

i have to go to work now, so ill get back to the thread in 10-12 hours, if the supplied pictures ain't good enough or you need me to measure something with my DMM tell me what and i'll do it as soon as i get online smile.gif

Thanks in advance

Tusore
post #2 of 9
You have been doing a good job so far.
Looking at the FB pin I would continue following the pathway to find another soldering spot to reduce risk of a possible damage if something goes wrong.

To be completely sure about voltage measuring points a pic of the front of your card would be nice: http://www.overclock.net/attachment.php?attachmentid=199672&stc=1&d=1299912338

Always try to measure voltages at any kind of capacitors - at inductors(input side) you'll usually get larger values.
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post #3 of 9
Your on the right track..and the VR size will do perfectly wink.gif

Heres another RT88** mod..

4850_modcans5.jpg
4850_modcans3.jpg
post #4 of 9
Thread Starter 
yay biggrin.gif!!

i got my hands on a set of 2 55K ohm VR's today, so i decided to do the volt mod.

even though the solder iron i used had a tip the size of a thumb i managed to do the voltage mod, it wasn't pretty, but it works non the less smile.gif

img3613qi.jpg

and another one of the full board

img3611w.jpg

i am currently running 820 core and 1935 on the shader processor opposed to a default 600/1500 i haven't tried to adjust the memory yet and i don't know how far the clocks will go as i haven't really tested it yet.
post #5 of 9
Thread Starter 
does anyone know if it's possible to add a atx 6 pin power cable to the gfx? as far as i know the pci-E slot only allow you to draw up to a maximum of 75W of power. would it be possible to solder a connector to the gfx, so that i could supply the card with some extra juice. I see that the pcb has the layout for the 6 pins and when testing them with my DMM they seemed to be connected.

also, does anyone know how much voltage i can apply to GPU without it dying immediatly? so far i am sitting at 1.3 Load and it doesn't get too hot Imo.

I would also like to try and mod the memory voltage, so if anyone could help me mod memoryV i'd be thankful.

i'll upload some pics of what i suppose is the IC for memory voltage aswell as some pics of the frontside of the pcb. if it has any relevance the ram modules on my gfx are samsung ones

img3615.jpg

the text on the IC says "p6161s14" and "VDK93R"

img3617.jpg
post #6 of 9
Measure resistance between pin 4 and 7 of uP61616.
Samsung GDDR3 will clock better with higher voltages thumb.gif

Adding a PCI-E power connector is probably just the half story. There are also some other components missing which would have been there. For example an input(12V) inductor and capacitors. You can also see empty pads for MOSFETs/inductors/capacitors of the GPU power circuit.
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post #7 of 9
Thread Starter 
hmm okay.. do you think i'll be reaching my limits through the lack of power from the pci-e slot or do you think the card will be the limiting factor? what would happen if i tried with the atx 6 pin, would i fry the circuit???

i measured the resistance between pin 4 and 7 which gave me a reading of 570 ohms smile.gif
post #8 of 9
Get a 20k VR(or bigger) and solder it between both pins.

You will be power limited. Actually I'm wondering that you haven't passed the 75W already. Nvidias 8800GT (which is basically them same) has got a TDP of 112W iirc...

I am not sure what will happen. The power might stop at the empty MOSFET pads or before but could also damage other components.
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post #9 of 9
Thread Starter 
well i'll give the memoryV mod a try tomorrow then smile.gif

i kinda knew the power would be my limitation, but thats just how it is biggrin.gif

the card was a cheap 100$ card that i bought 1½ year ago as a replacement for a 7600 gt, so any gained performance is worth it biggrin.gif.

i did this mod because i wanted to try it, as i didn't really need the xtra performance for the games i play.

i'll post my results when i am done besides that i consider this thread closed biggrin.gif

thanks for the help especially you mAlkAv!An and all the other contributors on ocn biggrin.gif
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