Overclocking gtx 970 glitches

[Tom 1993]

Hi all,

I'm trying to get a stable overclock on my Gigabyte g1 gtx 970 gaming 4g gpu. After some benchmarking and adjusting mhz I got to 1475 mhz core clock and 8100 mhz memory clock. When I run unigine with this I get all kinds of graphic glitches. Green squares and such. Is this a voltage problem? The problem is now quite gone, 1475mhz & 8000 mhz with 1223 mV. is this a safe voltage? thanks!

 

[Tom 1993]

If my heat doesn't ever reach 70 degrees, can I test around with the voltage safely, if I monitor heat at all times?

 

[jordan1794]

Green flashes and stars mean you are pushing your VRAM too much, you either have to lower the frequency or increase the voltage
(But most 970's and 980's are limited to 1.25v, even with software like EVGA precision)

Green squares/stuck pixels/blocks means you are pushing your core speed too high...again, either lower it or increase voltage.


The best practice is to increase one at a time until you see these glitches, called artifacts, then once you have found the MAX for each try a combination of the two...you will NEVER be able to achieve the max for each at the same time, so you will need to lower each one in turns until you get stability again.

Here is a screenshot of my spreadsheet when overclocking my 980:
(This was before I modded my BIOS and started changing my voltage)

 

[jordan1794]

& This is from after I modded my BIOS and increased my voltage:

 

[Tom 1993]

Thank you very much for this answer. So I'll put my voltage on 1250 since that is the limit you say, then I keep adjusting the memory & core speeds till I don't see any artifacts anymore? Thanks again! Nice speeds you got there!

 

[Tom 1993]

& This is from after I modded my BIOS and increased my voltage:

Thank you very much for this answer. So I'll put my voltage on 1250 since that is the limit you say, then I keep adjusting the memory & core speeds till I don't see any artifacts anymore? Thanks again! Nice speeds you got there!

 

[jordan1794]

As long as temperatures are good 1.25 SHOULD be safe, but as with all overclocking do so at your own risk.
With the Nvidia cards they will lower the clock speed when you hit certain limiters. The newest GPU-Z will actually tell you what limiter you are hitting(you can see the codes and their meaning in my spreadsheet)
Generally, you will always see vRel when running, this is telling you that the only thing holding you back is voltage, because in theory you can always increase voltage to get a higher speed...that is, until you hit the voltage cap...at which point you will see TWO codes,vRel and VOp, telling you that you COULD go higher if you could get more voltage, but you CANNOT because you are at the voltage limit.

Although in your case you will most likely run into a different problem first...Pwr...
The Nvidia power limit is pretty easy to hit, when I modded my BIOS I actually did NOT increase my voltage limit, I just upped the power limit...
With 1.3v I could probably hit 1600 MHz rather easily, along with going over 8500 MHz on my memory, but it's a pain to change it and I always get nervous when messing around with the GPU BIOS, 1.3v because the card is PHYSICALLY limited to 1.3v, no BIOS mod alone can go over that...the card also has a PHYSICAL power limit separate from that set in the BIOS, you can do certain hard-mods to remove this as well, but that is getting into the VERY extreme overclocking areas...you won't have to worry about the physical power limit unless you are BIOS modding for 1.3v and an upped BIOS power limit.
I myself have yet to hit the physical limit.

If you hit the Pwr limit make sure you have the power target set to max, be it Precision or afterburner...
While running without a BIOS mod you may actually find you can maintain higher speeds if you do NOT up the voltage.
This is because Wattage (power) = Amperage x Voltage.
Increasing voltage increases power, meaning you will hit that power limit even more quickly.
You may get a higher initial clock speed with more voltage, but end up downclocking and performing worse because you are hitting the power limit more quickly.