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Printed On: | September 8, 2008, 7:45 pm |
| Category: | Overclocking | |
| Type: | Guides | |
| Posted By: | yantronic | |
| Date Posted: | May 8, 2006, 2:13 pm |
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Voltage Modification On GPU
Recently, we got our hands on a piece of 7600GS from Inno3D. Based around the NVIDIA G73 GPU built on 90 nm process, it promised much headroom for overclocking.
The 7600GS arrives!
Based on the 90nm manufacturing process, the G73 promises much headroom for overclocks.
Initial tests were promising enough, for we hit 470MHz on the GPU and 460MHz on the gDDR2 memory without making any changes to the card. As you all know, we can turn into clock-hungry demons when the benchmarking addict is unleashed after a period of dormancy, so... ...
The Inno3D 7600GS is based upon NVIDIA's P345 PCB design.
On close scrutiny, we were able to work out the Voltage Modifications for both the memory and GPU voltage.
U505 forms part of the voltage regulation circuitury for the GPU.
The ISL6549 is used in both Vgpu and Vgddr2 voltage regulation. We will be looking at pin 4 of the ISL6549. Take note that the indent is beside pin 1.
In order to increase the Vgpu, hook a 50kOhm potentiometer from pin 4 to ground. Decreasing the value of the resistance between pin 4 and ground get your Vgpu up.
Vgpu values are available on the inductor L9. You can choose to measure either ends of the inductor as there is less than 0.1V of potential difference between the two ends.
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Voltage Modification On Memory
We didn't find the memory clocks sufficient to catch up with the GPU clocks and therefore decided to do the Vgddr2 voltage modification too.
2.5ns Hynix gDDR2 memory chips. 8 of them give 256MB of video memory for this 7600GS.
For the Vgddr2 modification, we set our eyes on U501.
Like Vgpu, Vgddr2 is controlled by the ISL6549 too.
Again, a 50kOhm potentiometer went between pin 4 and ground of the ISL6549. Decreasing the resistance between pin 4 and ground increases Vgddr2.
As there were no VTT and Vref modifications to be found, the Vgddr2 is believed to be auto-tracking.
Vgddr2, can be measured off either pins of L11.
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Test Clocks And Observations
Booting up sucessfully, we went on to experiment with the voltages.
Due to the increased heat produced, the original HSF was dumped for a beefier copper HSF, the Zalman VF700Cu. We are having a promotion on it (alongside higher and lower end models) for our forummers so do check it out here.
First, we tweaked the Vgpu from 1.1V to 1.8V and saw a massive clock increase from 470MHz to 720MHz. That is a massive 80% overclock over the 400MHz original!
Again we would like to emphasise that proper cooling is ABSOLUTELY NECESSARY for running at such high a Vgpu.
Hynix's datasheet stated a maximal Vgddr2 of 2.1V, so we raised it from the original 1.8V to the 2.1V region. Playing around, the stablest Vgddr2 was between 2.00V and 2.05V. At this voltage, the memory only went an extra 5MHz (10MHz effective). That put our memory clocks at 470MHz.
Our clockspeeds, set via ATiTool 0.25 Beta 14.
To test for stability, 4 instances of Real Time HDR IBL was run at the 1.8/2.05V and 720/470MHz settings for 5 hours straight. I then went on and launch Unreal Tournament 2004 for a couple of hours of fragging fun (editor! I ain't skiving!).
We gave 3DMark03 a spin on the 7600GS too, and saw for ourselves the beauty of increased fillrate abilities. Mother Nature hopped-up by ~20FPS and we had our Smooth Turtle!
These 7600GS sure are a hell lot of fun to play with and at slightly over SGD200 (USD100) a pop, it doesn't hurt the shallow wallets too.
Happy Clocking! :D
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