In Part 1, we had a look at the tools and the read points. In part 2, I completed and tested the voltmods. The next step was to strip off the stock cooler, insulate and install the VGA pot. Then get the card below0, increase the volts and see how far the Asus 8800GTX can be pushed.
WARNING: This article is not intended to be a volt modding guide but rather a log of my progress while doing the mods to the 8800GTX. If you do plan to give volt modding a go, you need to understand that performing these voltmods will void any and all warranties of your video card. You – and only you – are responsible for any damage caused indirectly (or directly) by any modifications made.
To refresh your mind, in part 2 I tested the card using the MSI BigBang XPower, an Intel i7 975 cooled with LN2 and the ASUS 8800GTX (only cooled by the stock cooler with the fan set to 100%) and I was able to reach 648mhz on the core, 1053mhz on the memory and 1674mhz for the shader clock. All of the above was with the vGpu and vMem volts at stock
Once the 8800GTX was down to a chilly -62’c provided by the DICE. I used the same method described in the MSi N480GTX Review, starting with the vGpu I would increase the speed 25Mhz at a time until Kombustor would artifact or the PC would crash. then I would decrease the resistance on the VR increasing the voltage and try again. At 100Mhz intervals I would switch and increase the memory speed in 25Mhz increments and again once I had increased by about 100Mhz switch to the shader clocks.
I managed to clock the vGpu to 916Mhz the memory to 1300Mhz and the shaders to 2100Mhz with 1.72v on the core and 2.250v on the memory. At these clocks there was no issues in Kombustor BUT now the true test, 3D Benchmarks.
Starting with Aquamark I quickly discovered that i was a bit over ambitious with the volts and the clocks, only getting 5 seconds into the test before the OCP/OVP kicked in. A little disappointed, I decided it was time to do a Google search. A couple of quick searches later, I found some great info. The 8800GTX/GTS cards OVP kicks in when the vGpu volts are above 1.6v.
With my new found knowledge thanks to the power of the Google machine, I needed to redo the overclock on the card. Setting the vGpu volts back down to 1.599v I was able to get 864Mhz on the core, 1269Mhz on the memory and 1782Mhz on the shaders. The vGpu was pushed as high as possible at the expense of the shader clock’s.
When running 06 and Vantage I lowered the vGpu and Memory clocks to 756Mhz on the core and 1053Mhz on the memory. the shaders were left at 1782Mhz.
Check out the screen shots below for the scores achieved at these clocks, worth just over 100 boints on the bot!
Part 3 was planed to be the last part in this series of adventures with the 8800GTX but my discovery of the OCP/OVP while benching has brought Part 4 to life.
Whats coming in Part 4 you may ask? Well starting with the OVP, I will need to change resistance between ISEN’s for each phase by putting in parallel extra 1.5kohm 0603 resistor on top of capacitor on the RCR-circuit. By doing this I will reduce the voltage reported to the PX3540 controller removing the OVP. I will then need to add a 100k VR to ground on the resistor connected to the VMAX pin of the PX3540 controller for the OCP mod and For good measure I will be adding Low-ESR polymer capacitors to the power phases on the front of the card to provide a cleaner supply of volts to the core/memory. (Thanks for the info TiN)
until next time Happy Benching…