HD7950 - FurMark - FPS drops

OlliL · Jan 20, 2013

Hi,

I have a Gigabyte HD7950 running at 1020 MHz.
FurMark Settings are:

Fullscreen [X]
Resultion 1280x1024

CPU is an i7-920@3.8Ghz

I notice massive FPS drops. Regulary the FPS is at 58FPS, but it drops down to 35/40FPS and then moves quickly up to 58FPS. This is of course also noticable right with your eyes. The drops can also be seen in the temperature of the GPU where it drops from 82° to 72° directly 1:1 to the FPS drops.

What can be the reason for those drops? I also notice such things in Guild Wars 2 but I'm not sure if its there because of my GFX or my CPU.

The drops start when the GPU reaches a temperature of 82°C
Before that, it is more or less fluent.

Could the CPU or RAM timings be a problem?

fluxlite · Jan 20, 2013

I assume the drop in FPS is accompanied by a drop in GPU usage? If so does the clockspeed or voltage go down, too? (I assume you have afterburner)

OlliL · Jan 20, 2013

Yes, the GPU usage drops then too.
The drops start when the GPU reaches a temperature of 82°C
Before that, it is more or less fluent.

The voltage in idle of the HD7950 is 0.950V.
Under load it is 1.250V.
Together with the drops, the voltage falls back to 0.950V and rises then afterwards back to 1.250V.

fluxlite · Jan 20, 2013

Yes, msi afterburner will show you GPU voltages.

That temperature is ok, these cards (contrary to what most people think) don't actually start throttling until over 100c.

Cards also throttle due to power consumption as well as temp to prevent damage, so this is a possible cause...have you increased max power in ccc?

Furmark is a very intensive synthetic bench - you will never find a game that stresses the GPU as much.

OlliL · Jan 20, 2013

Yes, I increased the Power usage to 20% which is maximum.
During the benchmark, the power consumption of the system raises up to 508W and then falls back to 446W during the FPS drops. My PSU is:

http://www.chieftec.eu/en/component/content/article/54-a-135-serie/93-aps-550c-550watt-80plus-kabelmanagement.html

Shall I reduce the Power Usage? Do You think my PSU is the problem?

fluxlite · Jan 20, 2013

Quote:

Originally Posted by OlliL

Yes, I increased the Power usage to 20% which is maximum.
During the benchmark, the power consumption of the system raises up to 508W and then falls back to 446W during the FPS drops. My PSU is:

http://www.chieftec.eu/en/component/content/article/54-a-135-serie/93-aps-550c-550watt-80plus-kabelmanagement.html

Shall I reduce the Power Usage? Do You think my PSU is the problem?

How are you measuring power usage? If it's at the wall then remember that there's a difference between how much the PSU is drawing versus how much the PSU is throwing into the system (based on its efficiency).

50A max draw on 12v seems enough - 7950 will pull about 160W overclocked in furmark I reckon. Depends if you have a billion other things in your pc.

Another possibility is that the chokes and power regulation on the card can't feed enough power to the core. Does it still fluctuate on stock?

OlliL · Jan 20, 2013

At the wall, yes - so lets assume 80% less.

I reduced my CPU Overclocking now from 3.8GHz to 3.6Ghz (Multiplier 21->20)
GPU is now configured with 1000 MHz GPU Frequency (shipped frequency):

+10% Power consumption
- the GPU runs at 900MHz
- FurMark appears to be more or less fluent at 45FPS @81°C from time to time it drops to 30 FPS
- Power Consumption is around 450W

+11% Power Consumption
- the GPU runs at 900MHz
- FurMark FPS rises to 46FPS but with drops to ~30FPS and back.
- VIN0 of my HD4950 stays at 1.250V during this drops.
- Power consumption of my System also drops from 465 to 380W during the FPS drops.
- GPU Usage stays at 99°

+12% Power Consumption
- the GPU runs at 900MHz
- FurMark FPS rises to 49FPS but with much more frequent drops to ~30FPS and back.
- VIN0 of my HD4950 stays at 1.250V during this drops.
- Power consumption of my System also drops from 470 to 420W during the FPS drops.
- GPU Usage stays at 99°

Components in my PC:
- 2 Harddisks
- 1 DVD-ROM
- 1 DVD-RAM
- USB G35 Headset
- USB Hub with independent Power -> USB Mouse + Keyboard
- 1 PCI SCSI Controller
- 6*4GB DDR-1333 RAM

Edit: +8% Power Consumption apears to not cause any FPS droppings @41FPS @440W

OlliL · Jan 20, 2013

When I clock the CPU back to 2.60GHz which saves me around 50W Power Consumption, I can move the Power Consumption of the GFX to +9% with FPS drops only once every minute.
The System then uses 426W at the Wall.

Edit: I can change the frequency to 1020 lets say, but shortly after applying it the FPS moves to 52FPS but then immediatly the frequency always falls back to 900Mhz.
Only when I change the Power Consumption to a quite high value, the frequency moves to the desired value but then with the drops.....

Edit2: When I put the card into my wifes PC (AMD Phenom II X4 965) I can move the Power Consumtion without drops to 11%@46FPS by having 400W Power Consumption. The PSU is the same as mine but the base power consumption of the AMD system is less than my i7

Edit3: Back at My i920@2.6Ghz: When I remove the DVD-ROM, DVD-RAM, 2nd hdd, 12GB of RAM, SCSI Controller, I can set the Power Consumption to 13% which brings me 50 FPS without FPS-drops. I'm then at 415W

Conclusion.....PSU?

HD7950 - FurMark - FPS drops

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