Lower stable overclock at 4k than 1080p

[Tacitus]

I asked elsewhere but didn't receive a good explanation.

I have a 290x PCS+ which runs for hours at 1080p at 1150/1450 with +50% power and +75mV. Temps are mid 70s on both core and VRMs. The VRMs and VRAM modules both have heatsinks. Temperatures are not the issue.

At 4k, such settings crash the game/my PC within a minute.


It seems that when I touch power/voltage it becomes very unstable and I don't know why - temps are actually lower since I can't get anywhere near as much extra power/voltage, and I've had to scale back my OC to 1075/1400.

GPU usage is 100% in both scenarios.

Is this normal, and why is this happening?

 

[BinnsY]

I'd imagine it's because you are asking your graphics card to work much much harder at 4k than you are at 1080p. Even with GPU usage at 100% you will have a lot more graphics memory in use at 4k meaning the card has more to do.

 

[Tacitus]

I'd imagine it's because you are asking your graphics card to work much much harder at 4k than you are at 1080p. Even with GPU usage at 100% you will have a lot more graphics memory in use at 4k meaning the card has more to do.

Would more power not help, rather than hinder, in that case?

Should I see if a bigger memory over clock helps?

 

[Aretak]

Was the same with the two 1070s that I had. Overclocks on both became unstable at 4K (using DSR in my case). The Fury I have now doesn't seem to care though, although I only have it at 1090MHz on stock voltage.

 

[Kaapstad]

4K is a lot more demanding on the GPU.

Just because a GPU will run at a clockspeed @1080p does not mean it is working flat out all the time. At 4K where the images are bigger the GPU takes longer to render them and spends more time flat out.

Power consumption also goes up @2160p for the above reason and I even had to upgrade the PSU in one of my PCs to cope with it.

 

[Kaapstad]

I'd imagine it's because you are asking your graphics card to work much much harder at 4k than you are at 1080p. Even with GPU usage at 100% you will have a lot more graphics memory in use at 4k meaning the card has more to do.

Exactly.

You can get away with a dodgy overclock @1080p where the frames are quick and easy to render but it catches up with the GPU @2160p.

 

[Tacitus]

These explanations are much more useful than what I got elsewhere.

So in short, expect a lower overclock and it's unlikely something is wrong with GPU/Monitor or both?

 

[BinnsY]

Indeed. Although you can shove more power into your GPU to try and compensate for it eventually you will hit a point where even with the power it just can't phsyicall do it. One of the thosands of calculations it's doing will go slightly wrong and you will get unexpected behaviour. At 4k it simply has an awful lot more to do and there is more chance of one of those calculations going wrong.

 

[passey89]

I get exactly the same on my 980ti and now on the 1080.
Think I need a better PSU anyway though tbh.

 

[Tacitus]

Indeed. Although you can shove more power into your GPU to try and compensate for it eventually you will hit a point where even with the power it just can't phsyicall do it. One of the thosands of calculations it's doing will go slightly wrong and you will get unexpected behaviour. At 4k it simply has an awful lot more to do and there is more chance of one of those calculations going wrong.

But is it not strange that adding power/voltage causes instabilities, even at stock clock speeds (which are stable at stock power/volts)?

 

[Nasher]

Boost clocks are probably slightly unstable. This seems to be very common on factory OCed cards. They don't put a cap on the clock speed and only seem to regulate things with voltage. This means if you up the voltage, it will also up the clocks :/

I had it with a 970. It's fixable, but you have to enable to the boost cap on the card and set it to something you know is stable. Which means altering it's BIOS.