What variables/hardware affect a GPUs overclock limit?

jesusjones1024

Honorable
Apr 11, 2013
6
0
10,510
HELLO all! Recently I realized my decision five years ago to donate half my brain to science (aka buy a xbox360) has been a lessthanfruitful ride filled with lackluster gaming and quality compromises only reserved for my future marriage(s). So being a CS junkie since puberty, I finally got the gull to buck the convenience and get back into PC gaming and damn if it aint a beautiful feeling!
Here is my current build pieced together from an older dell xps:

MidTower XPS (bent to ish to fit cooling :D)
Chipset: i7 860 2.8 (sometimes OCed to ~3.6)
GPU: His 7950 Iceq x2 Boost 3gb
Memory: 8GB DDR3
HDD: 1tb
PSU: OEM 750w
OP: Windows 7 Ultimate
Cooling: Corsair H70

I am currently 3 months into my project and for the most part, late nights on google (and toms) have told me what i need, how to get it, and more importantly how to use it.
Choosing my new GPU has been by far the hardest decision because when im not music editing, i will be gaming.

Yet finally my first major hiccup has arrived. I cannot for the life of me get my 7950's core stable above 1050mhz. Ive read many guides on how to use gpuz to monitor, and msi afterburner/iturbo/asus to change core and voltages. But as soon as i run heaven or kombuster to benchmark (or even sometimes ingame) it will start for a while, then crash and restart. My temps dont go higher than ~ 75c full load with a 120mm fan jimmy rigged like an accelero.

Now i dont think im greedy asking the 7950 to go 115mhz over its base when so many people online are going wayyy higher= http://www.techpowerup.com/mobile/reviews/HIS/HD_7950_X2_Boost/33.html
^1210 mhz

I already RMAed a EVGA 660ti, (another story, "artifacts" belong in the museum eh??) and i really dont want to RMA this card unless i know for sure.

So whats your thoughts?

Could it be my motherboard doing some weird power surging or its lack of pci e 3.0? http://forums.extremeoverclocking.com/t363657.html

Could it be my cpu bottlenecking? http://m.tomshardware.com/reviews/gaming-processoror-frame-rate-performancerepublicans,3427-5.html

Mainly what variables really affect a GPUs overclock limit? Why can so many different people have such different OCs for the same card? Any and all suggestions are welcome!! My GPU choice is already decided based on my $ range so pleeeease no fanboy comments - u guys make republicans and democrats look like teeballers.

Thanks ahead of time. Its been bugging me so bad im sending this from my phone while on vacation in hawaii. Haha...sad.

Okay, ready? Goooooo
 
There are no overclocking guarantees to any graphics card, all hardware is different, some are just better quality parts the card was assembled with, you can have 2 identical cards from the same manufacturer one overclocks well the other doesn't, so sometimes it's just the luck of the draw.

However sometimes the cards could actually be on equal levels hardware wise but the assembly process was done shabbily, meaning too much thermal compound was used on the GPU die or heat spreader, the thermal pads are only halfway covering the memory chips and voltage regulators.

Under those circumstances the card will run hotter, and seriously limit the overclock.

That would at least be your first inspection route to see what you have in hand, but you should never reuse the thermal pads always replace them as they are designed to seat in from heat, so always replace them.

You can replace the thermal compound on the GPU die or Heat Spreader with a high quality thermal compound, and get some suggestions from the thermal roundup in my sig.

So that's one possibility, an improperly applied heat sink cooling fan on the card.

You need to first eliminate that as a possibility, because if it all looks great under the heat sink, then it could be a better cooling solution is needed for the graphics card, or your case airflow needs to be improved to get the heat out of the case as fast as possible.

Some reach their higher clocks by also increasing the card voltage, I do not suggest that until you know for sure whats under the heat sink.

Actual experience example. > I have 2 580GTX that I decided to water cool with full coverage water blocks, both cards were EVGA, when I pulled the first heat sink and inspected under it I was amazed and thoroughly pleased, the thermal application was almost perfect, the thermal pads were all properly placed and aligned.

So naturally I was expecting the same quality of application on the second 580, but was literally shocked at what I discovered under the 2nd heat sink, the thermal compound looked like it had been applied with a caulking gun, wayyyy to much thermal compound, the employee that assembled that cards heat sink could have done 5 cards with what he or she used!

None of the thermal pads were properly aligned and two were only half covering the memory chips, I was thankful I had not overclocked either of those cards yet!

That card looked like the heat sink had been installed by a drunk monkey, or by an employee that did not care, or was improperly trained in the heat sink application on the card!

A thermal compound application on a GPU die or heat spreader needs to be as little as possible for full coverage absolutely no excess, because too much thermal compound will insulate instead of conduct heat.

So in all actuality before you even consider overclocking any graphics card you should know for sure the heat sink is properly installed on the card.
 

jesusjones1024

Honorable
Apr 11, 2013
6
0
10,510
I knew i needed my own thread cause your input is exactly the kind i havnt found on my own! Very interesting idea and i do love getting my hands dirty, so reapplying the thermal compound and seeing whats in this baby is right up my alley.

Two things i noticed from your sig on thermal paste:
1) You mentioned wanting to avoid voiding your warranty on the cpu. Ive only had my card about a week so its definately still in the 30 days, but will doing what you suggest void it? Will they easily be able to notice? Im guessing no but i dont want to break any unknown seal.

And more of an aside but 2) Watercooling my cpu now looks overrated according to your charts haha
 


1), You're not going to void a warranty with normal thermal compounds that statement was in regards to the liquid metal compounds which I do not suggest using because removing them is almost impossible to do without scratching the heat spreader or die.

The best thermal compound I tested was the Timtronics Grey Ice 4200, FrozenCPU also carries the Thermal Pads.

2), Water cooling vs Air Cooling a CPU, in all actuality a Big Air or high end heat pipe Air Cooler, performs as well as a mid range water cooling setup, they are both dependent on ambient room temperature air.


 
FYI: Underneath your graphics cards heat sink you'll discover two thickness of thermal pads, the memory chip pads are thinner than the voltage regulator pads.

The bottom three on this page is what I suggest you buy in advance, the three different thicknesses will assure you have what you need on hand to do the change out and match what's on the card, it's better to have it and not need it than to discover you don't have the proper thickness pad to replace.

You can cut these pads to fit and they have removable protective surface film on each side you remove when placing.
 

jesusjones1024

Honorable
Apr 11, 2013
6
0
10,510


Perfect. Cleared up MY worries. I actually lucked out that the artic cooling mx-4 performed admirably on ur test considering i just bought some for my h70 install. So ill probably save the money and use that unless theres any objections?

Okay feeling better already. Not leaving here till saturday but im excited to get home now and get to work. Ill keep you updated. Thank you for your input and your time!

Edit: just saw your recommendation on the pads. Ill order them now so theyre there for me when i get back
 


Artic Cooling MX-4 is an excellent compound, absolutely use that!

 

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