Contents

• Intro
• Turbo Boost 3.0
• Cooling compatibility
• STEP 1 – Prep your bench
• STEP 2 – Get card ready
• STEP 3 – GPU Voltage trim-pot mod
• STEP 4 – Memory voltage trim-pot mod
• STEP 5 – PLL Voltage trim-pot mod
• STEP X – BONUS

Intro

This is not another GTX 1080 Ti review, but a extreme overclocking modding guide. There is no much benefit doing all this for watercooling or aircooling, but required when GPU is frozen to chilly -196°C. Fair bit extra voltage might help reaching higher performance marvels.

Image 1-2: Introduction to GTX 1080 Ti GFX overclocking

This guide is evolution of my usual “uncork series”, with all good traditions set by previous guides:

• Reference GTX 1080/1070 – Uncorking Pascal
• Removing power limits on any NV card
• Using Raspberry Pi to control your VGA VRM
• EVGA GTX 980 Ti K|NGP|N OC Guide
• Reference GTX 780/780Ti – Big KEPLER
• EVGA GTX 680 Classified – Uncorking guide
• Reference GTX 680 – Uncorking KEPLER

Let’s study plain reference EVGA GTX 1080 Ti which is also called “founders edition”. This is the baseline card, which we all get to know first before going any specific custom board designs.

As usual, you are on your own alone, even when doing even little simple mod. If you card/system bursts in flames or just simply stop working, do not try to RMA it or expect a support from manufacturers. Anything below this paragraph in this article is NOT covered by any kind of warranty, and provided AS IS only for education purpose, without support from manufacturer or NVIDIA. So yes, “don’t try this at home”. Any RMA attempt of soldered card is easily diagnosed today and will be rejected.

No doubt, modifying your GFX for benchmarking and records require bit of above-minimal soldering skill knowledge and cold mind and sharp eye. Entry-level things, such as how to probe voltage/resistance with multimeter, what is trimpot and how to solder piece of wire, as these things were explained over the internet thousand times already and easy to google. If you need more info – also check previous guides, linked above.

Interesting to see NVIDIA’s return on nerfing memory bus width by unpopulated memory chips on fully routed 384-bit memory bus on PCB. That’s happening because reuse of PCB from Titan X (Pascal) card. There is no much point to respin new PCB design, since both Titan X Pascal and GTX 1080 Ti have same package and essentially are same thing, just different configuration of active blocks. This is not a new trick, we saw it years ago on cards like GeForce 8800 GTS and GeForce 9600 GSO, and others. Photo below shows old 8800 GTS card, which I had some 10 years ago. That card had 320-bit bus, derived from full 384-bit GeForce 8800 GTX full G80-based design.

Image 3: Back to future, EVGA GeForce 8800 GTS ACS³ KO with removed memory chips

And no, it’s not unlockable even if you put BGA memory chips on the PCB. This is hinted by -K1 code on GPU die, which hints on disabled memory controller. Same Kx marking was present on G80 above too ;).

Okay, let’s find out what color of smoke is hidden inside bigger GP102 Pascal 16nm GPUs!

Turbo Boost 3.0

Updated Turbo Boost is same one used in GTX 10xx series cards, so all same rules apply.

Different ways of overclocking

There are two main ways how power users overclock their hardware. Few words about this are necessary to further comply with overclocking approach on Pascal GPUs, which also include 1080 Ti.

Max performance for everyday use – users who mostly care about practical overclocking fill in this method. This means getting most of performance possible with keeping low power management, low acoustic noise levels and reasonable power consumption. Such users often use aftermarket cooling, like water-blocks to get most from the card while keeping maximum temperatures low. For this case new Turbo Boost 3.0 might be helpful to uncork those little bits of performance left in card.

Max performance at all costs – this is where hardcore benchmark and extreme overclocking folks lurk. Usually involves subzero cooling, completely removing thermal limitations from the card operation. Power limit modifications help to avoid hitting performance cap from the power monitoring. Avoiding worry about temperatures and power simplify things a lot. And since for this case we just want maximum performance at all times, there are no benefits from Turbo Boost 3.0 here.

Now with this short intro of both cases we can get a grasp on new controls. On Pascal now it’s possible to adjust not only GPU clock offset to the all GPU states, but adjust offset for every specific VID range. As part of power management tech on NVIDIA cards since very first GeForce cards, GPU have ability to control its voltage. According to different GPU usage levels power regulator output is adjusted on real-time to get lowest possible voltage for desired frequency. This translates to a voltage/freq relationship, which can be shown as table of values with multiple points.

On pre-Pascal GPUs we can add offset to desired GPU frequency which is being applied to all frequencies in V/F table. But actual maximum frequency of specific GPU can be either lower on specific voltage points (this will make card crash and get stability errors/artifacts) or higher (meaning card could be faster, but capped by fixed GPU offset/volt table). Turbo Boost 3.0 on Pascal now allows you to control each point, to get the most performance possible. So new version allows you to play with everyday overclocking knobs in more precise manner, but does not change much for extreme “all-out” overclocking cases.

Cooling compatibility

Many of enthusiasts always worry if their current water/chiller or LN2 cooling system will still be useful for fresh new hardware, such as GTX 1080 Ti. Worry no more, mount hole locations and clearance is exactly same as 680/980/980Ti reference cards. Previous generation GPU coolers will fit new card fine, if not constrained with VRM area coverage.

Image 4: Cooling hardware

STEP 1 – Prep your bench

Will need set of common tools for successful modding of reference GTX 1080 Ti card, which is similar to any other VGA.

• Card itself. EVGA GTX 1080 Ti FE used here to play with.
• 1 × 5 KΩ multi-turn VRs (trim pots) for GPU vmod.
• 2 × 50 KΩ multi-turn VR (trim pot) for memory and PLL mod.
• 3 × 10 Ω chip resistors, 0805 size. Example from Digikey, Mouser, Farnell DE for power limit mod.
• 25-45W soldering iron for trimpot mods, 80-120W for EPOWER.
• Roll of 28-32AWG insulated wire
• Soldering FLUX
• Kingpincooling TEK9 FAT
• DMM (I use fancy handheld Fluke 87V and high-performance Keithley 2002, but any 10$ DMM can fit needs of this guide)
• Low-ESR capacitors (2.5 or 4V rated, 680-820uF , etc) if you like to juice things up, but not required.

Image 5: Trimmer resistors and ceramic capacitors example

Since EPOWER connection to card this time is not covered, no need to use high-power soldering iron and pretty much any soldering gear you have on table will fit the task well.

I had used ERSA iCON-1 soldering station with to cover all below. 102CDLF2.4 tip covered all trimpot mods for this guide, with temperature set to 290 °C. Before starting with soldering, clean the usual mess on table, get all tools checked and ready, turn on enough lights to clearly see all those tiny parts on PCB. Worth to ensure enough space around, so you don’t knock other stuff by accident. Also worth to take a close look on PCB layout from both top and bottom sides, to get familiar with location of key components and design.

Image 6: GTX 1080 Ti VRM section on reference board

Design is fairly similar to previous refresh x80 cards from NVIDIA, such as GTX 780Ti/980Ti and Titan series. We have GPU in center with eleven Micron GDDR5X memory ICs around. DVI interface is now gone to give space for larger exchaust footprint. GPU bears GP102-350-Kx-A1 marking, which tells you it’s larger 102 series processor (to remind you, GTX 1080 based on GP104, Titan X Pascal use GP102-400, pro Tesla P100 with HBM – GP100), silicon revision A1. It was manufactured by TSMC Taiwan. GPU area is similar to previous generation processors, but have much more transistor gates due to much smaller 16nm FinFET node process. There are some 0201 decoupling capacitors around GPU die to help with power delivery. No hidden jumpers, traces or test points are visible on the package elsewhere, so nothing to worry about. SLI and PCIe connectors look exactly same as before, no magic there. For high 5K/8K resolutions and multi-monitor surround you might want to use new SLI HB bridges, which connect both SLI fingers in 2-way SLI setup.

STEP 2 – Get card ready

Remove cooler from the card, since access to both sides of PCB for modifications is required. This time NVIDIA did not use TORX-type screws, so usual Philips and suitable size hexagon driver will do just fine. Avoid using pliers as those little components and resistors around are very easy to get damage if tool snaps. You will need hexagon driver to remove nut-head screws which used to hold backplate and PCB together.

Better keep all those custom screws in secure place somewhere, so you can put heatsink back after you done if you will decide to do so. Remember, after soldering your warranty will be surely violated, as every RMA center will easily see non-factory soldering specks, even if you very careful.

Now graphics card is exposed and ready for some measurements and modifications. I’ll spare our readers from boring part of measuring various points to find out what we need and where different connections go, so we can jump right into good stuff, starting with removing power cap limitations.

STEP 3 – Power limit overrides

Often gamers and users are mistakenly referring to 6-pin or 8-pin MiniFit.JR connectors as 75W or 150W capable inputs. Nothing can be further from truth. These power levels are nothing but just way for NV determine how capable is used board hardware in terms of power delivery system. It’s imaginary target number and have nothing to do with actual power taken from connector nor power input capability. Software and NV BIOS will handle GPU clocks and reduce voltages if measured power hitting programmed BIOS limit (which can and usuall is different value than 75/150W per connector!).

If you intend to do serious overclocking and benchmarking, it may be required to trick power monitoring circuitry to report lower power reading, so you not run into power throttle. Also to make sure we are not at any physical limit of power connector itself, check Molex 26-01-3116 specifications, which have specifications both 13A per contact (16AWG wire in small connector) to 8.5A/contact (18AWG wire).

This means that using common 18AWG cable, 6-pin connector specified for 17A of current (3 contacts for +12V power, 2 contacts for GND return, one contact for detect). 8-pin have 25.5A current specification (3 contacts for +12V power, 3 contacts for GND return and 2 contacts for detection). This is 204W at +12.0V level or 306W for 8-pin accordingly.

Now if somebody tells you that 6-pin can’t provide more than 75W, you know they don’t understand the topic very well. It’s not the connector itself or cable limit the power, but active regulation of GPU/BIOS/Driver according to detection of used cables and preprogrammed limits. So now we getting to know how actual power measured?

Just like GTX 1080 FE card is also using already known Texas Instruments INA3221 sensor IC, which is triple-channel monitor able to measure voltage, current and power on +12VDC input rails using just few external components and current shunts. Current shunt is special type of resistor which generate little, but measurable voltage which closely depends on amount of current flowing thru it. Thus card can detect power consumption in real-time and adjust its clock speed and performance automatically to keep power within specified envelope.

You can find current shunts which are marked RS1, RS2, RS3 on PCB with black resistive element in center and often with R002 or R005 or 2M0/5M0 mark on top. Sometimes there are no marks, but look is always very similar, like a large rectangular flat part with two or four wide metal terminals. Usually these shunts are located very close to input power connectors before the main VRM circuitry. If we manage to reduce voltage signal (which is in linear dependance from current) from these shunts, then reported power limit will be reduced as well. Don’t do anything with these shunts, just understand what they are for. Common “modifications” like applying liquid metal paste or using pencil are bad idea, as they do not provide reliable and static resistance change. Pascal cards have also protection against under-reporting, meaning that GPU will be stuck in low power state if reported power is zero or around that.

Adding 10Ω 0805 size resistor on top of every larger ceramic capacitor next to INA3221 U26 will reduce power levels about x3 times. These chip resistors can be bought in usual electronics shop, or online at retailers like Digikey, Mouser. In worst case you still can use usual thru-hole resistor, but it’s not as convenient and you risking damaging caps or ripping traces off the board if you apply physical force on the joints.

I don’t show actual photo of this mod, as it’s nearly the same as in GTX 1080 case. This modification also very similar for all other NVIDIA cards, with bit more details covered here and here before.

STEP 4 – GPU Voltage trim-pot mod

First and usually most viable modification is one to adjust GPU core voltage. Often (but not always!) extra voltage can help to get better stability and higher clocks, given no temperature or power limitations are hit. Maximum available voltage thru software only control on reference cards are very limited, so hence you may need hardware modification to achieve higher voltages.

Here’s photo of GPU power controller U501, which is same UPI uP9511P used on 1080/Titan XP. UPI’s site is really obsolete and lacks of information, so I could only know from layout and probing around that this controller supports at least 6 phases, no digital interface or parallel VID code setting (no array of 6-8 resistors around to set VID voltage code). Also uPI chipsets are still use analog ways to control power regulation, so there are no firmwares for this PWM. This also mean all protection settings like OCP/OVP are done by hardware and external components.

But no worries, by tracing where GPU power signals come around chip voltage sense lines were quickly found. These are two lines from resistors near D501 and Q502 location. Enough to know for us to do the voltage mod!

Prepare VR’s, in this case one 5 KΩ nominal resistance multiturn variable resistor (potentiometers). I like to use very common blue square 3296 type. There are many electronic components retailers have these available for sale, and it should be easy to find suitable resistors from your local store.

Now remove two resistors marked in red box on photo below to enable adjustment on feedback sense.

Glue 5 KΩ trimmer on the PCB like shown on photo below, to make sure it does not rip off or short anything later on. Sometimes I also use 2-position jumper pins to add ability of disabling mod to get stock voltage on the fly. That could be useful for troubleshooting later. Two AWG32-28 wires will be needed to connect trimmer to specific points.

Image 7: Example location of all three Vcore,VMEM,Vpex trimmers

Middle pin connected to point on top pad of removed resistor. Other trimmer pin connects to ground. Make sure you set resistor to maximum value (resistance measured by DMM across both wires, not connected to anything), which should be around 5 KΩ. Not a good idea to boot card right at the maximum voltage! Solder wires to tiny spots near GPU voltage controller (uP9511P IC on the bottom side of the board).

Image 8: Connection points of trimmer to raise GPU voltage

Since traces and solder points on PCB are very thin and easy to peel off, make sure you fix the wire to PCB in few places, so it does not move. I found use of few cyanoacrylate superglue drops on areas free from components good enough. This will ensure modification is safely secured and will not rip apart tiny components so easy.

You can go as high as 1.5+V with this kind of modification easily, so it does also can be suitable for extreme overclocking. New 7-phase VRM can provide plenty of power for card, even when pushed over 2400MHz on GPU.

Note that GPU resistance on Pascal GPUs is very low, opposite to many previous GPU generations. I measured it around 70-150 mΩ (that is 0.07-0.15 Ohm), depending on GPU sample. Measurement was done using four-wire resistance measurement method with expensive high-accuracy Keithley Model 2002 DMM.

If you plan to use waterblock or Kingpincooling TEK9 LN2 container as GPU cooler, make sure you have good 120mm fan over VRM area to ensure good airflow and acceptable temperatures (best under 70°C) when overclocking. 1080Ti’s PG611 reference design PCB have all seven phases fully implemented for GPU power with two PowerPhase arrays on each phase.

STEP 5 – Memory voltage trim-pot mod

Memory VRM using single phase, with same as Vcore VRM PowerPhase dual NFET and output fixed 1.35V for GDDR5X memory chips.

Image 9: Modified memory circuit to raise voltage

To raise voltage all you need to do is just 50KΩ trimmer to GND at marked point.

STEP 6 – PLL Voltage trim-pot mod

PLL regulator is common and known from previous GPUs, so nothing new here. PWM chip used is uPI UP1628Q in tiny DFN package. Modification to raise voltage on it is straight forward and involve connection of 50KΩ trimmer to GND and point on the photo above.

Image 10: Connected trimmer wire and monitoring point

Monitoring of PLL voltage output can be done by soldering wire to location of three resistors near bottom left GPU fan-sink mount hole.

Now everything is finally ready for some serious testing. Make sure you start with little voltage adjustments first and note all steps as you go higher and higher. This will help you to understand how voltages and things affect stability and make further overclocking easy.

End result might look like this:

Image 11: All modifications in place

With trim pots wiring. You can see blue wire to connect ground at unused power connector.

Image 12: All modifications in place

STEP 7 – Remove thermal protection

To avoid losing power doing LN2 overclocking when GPU temperature can reach below -50°C, remove D508 component, located on the bottom side of the board near the GPU power controller area.

Image 13: Lift D508 leg or remove it to block GPU power protection

Warning! This modification essentially removes thermal protection mechanism, and in case of overheating GPU will be permanently damaged. Always make sure your cooling solution is installed correctly.

STEP X – BONUS

Extreme overclockers often like to put some brutal bodges over their cards, so here are locations to add more capacitors:

Image 14: 8-point mount of LN2 container on GTX 1080 Ti and probe points

Best to have full 8-points brackets to ensure good and even mount pressure across all GPU sides. It’s compatible with all TEK9 FAT and TEK9 SLIM containers and can be bought separately on Kingpincooling.com shop

Electrolytic and tantalum capacitors are POLAR devices and must be soldered in proper polarity, positive to positive, and negative to negative. Or big fireball and unrepairable damage can occur to your hardware.

Image 15: Do not solder polar capacitors in wrong polarity!

Extra capacitors may or may not help to push higher clocks. Up to you to find out that.

Check again, if everything good, no shorts on the card or damaged parts, solder blobs or dirt. Make sure all trimpots are set to proper value.
Assemble your cooling solution to a card, test voltages and give it a spin on overclocking, using EVGA Precision XOC 16.

Also here are reference points, key resistance values measured with high-accuracy Keithley 2002 DMM on good working card:

Voltage rail	Resistance measured	Nominal voltage
NVVDD	50-150 milliΩ depends on card	0.62 VDC … 1.07VDC
FBVDD	~50-80 Ω depends on card	1.35 VDC fixed
PEX	~40-70 Ω depends on card	1.01 VDC fixed

Table 1: Nominal resistance on main power rails from good GTX 1080 Ti card

If you get very different (less than 30 mΩ) resistance readings, you card is likely borked and game is over.

As usual, any feedback and questions are appreciated. Feel free to share link to this guide, but keep links and references intact, as guide likely to be updated in future.