XFX HD7950 Overclock

Gbear

Got my spangly new PC built a few months ago. It's running everything quite easily at the moment but I've a 1440p monitor and Crysis 3 on the way so I want to get the best performance I can.

XFX HD7950 (not the black edition).
ASRock Extreme 4

I've installed MSI afterburner.
Without an overclock (800MHz Core, 1250MHz Memory) at idle it's at about 48C.
Under full load using Kombustor it plateaued at 69C.

Are they normal?
I just want to be sure that seems ok and air flow is sufficient before I get to fiddling.

I've tried reading up a bit online but I'm still not really sure what overclocking entails. Do I need to adjust all the sliders or can I leave voltage and power limit alone (given that they seem a bit more hazardous)?

BloodBath

Those temps are pretty high for those clocks.

What case are you using? Is there a side fan blowing fresh air on the card? Is that the dual fan xfx or the single. How fast does the fan get at load?

You could overclock it some but at those temps you don't have much overhead.

You need to try keep it below 70-75c under load. These cards tend to get unstable if higher than that when overclocked.

First you want to disable overdrive in CCC. Then turn up the "board power li" in afterburner to the max of +20%. This allows the card to use more power when it needs to. It does not change the voltage's on the gpu or memory.

Change the settings to make sure all settings will be restored on booting, restoring ect. Reboot.

Now see how far you can go without changing voltages. Just leave the board power at +20%. Start with the gpu clock. I'd start at 1000 and test with a benchmark like Unigene Heaven and test it for stability. Monitor your temps with HWmonitor. It will record all your temps while the benchmark is running. Up the core by 25mhz each time and keep testing until it becomes unstable and stays below 75c. Instability will result in either the graphics driver crashing or the whole system crashing.

Check your fan profile in afterburner and adjust it to be more aggressive if it's fairly tame. You can make a custom profile that will adjust fan speed depending on how hot the card gets.

If you can keep it cool enough you should be able to get to 1000-1100 or so without increasing the voltage. They can go to 1200+ with voltage increases but temps will be the problem. You can go as high as 1300mv with the gpu voltage but unless you sort your temps I wouldn't touch the voltage.

Once you have your highest stable gpu clock start overclocking the memory. 1250 is a pretty low starting point so I'd start the overclock at 1350-1400 and go up in 25mhz increments until it becomes unstable. Test and monitor your temps each time. Keep an eye on the vrm temps as well and try to keep them below 80c. 1500+ is usually possible.

Gbear

BloodBath wrote: »

Those temps are pretty high for those clocks.

What case are you using? Is there a side fan blowing fresh air on the card? Is that the dual fan xfx or the single. How fast does the fan get at load?

Thanks.

My case is quite small and it does look pretty cluttered inside.
It's a Coolermaster Gladiator 600.

it looks a bit like this but messier because there's cables all over the place and I've nowhere to put them and the GPU is bigger:
It has no side fan. A new case is next on my shopping list but I didn't want to get one right away if I could avoid it.

Gbear

I've ordered a new case. I'll bump this when everything is put together (hopefully early next week).

Gbear

Right. I had the PC put back together (and my new Shimian monitor plugged in) by last Thursday but my internet crapped out on me.

In the mean time I decided to have a go at some overclocking.

With the new case GPU temp is about 25/6C idle - a serious improvement on the 48C that I was getting before.

I've started off slow enough with a 950 core and 1350 memory overclock.

It's holding steady enough although there's a bit of artifacting going on when I play Sleeping dogs (1440p AA turned off). Aside from that it looks magnificent.
After some fiddling around with the fan I've managed to get a stable 62C at full load without the fans getting too deafening - about 70% speed I think.

I'm currently downloading Unigene Heaven.

I'm not really after overclocking just for the sake of it.
I want to get the most safe most, stable performance without the fans having to make my eardrums bleed.

Gbear

Right so now that I'm a bit more comfortable with OCing I want to start fiddling with the voltage and maybe see can I take things a bit further.

Running Unigene Heaven - how long should you leave it run for?
I ran it at 1000 Clock 1350 Mem and it crashed immediately. Is that what should be expected?
For the moment under load the temperatures aren't getting any higher than 63C so I think I have a bit of wiggle room in that regard. The fan is set to run faster more or less exponentially from about 50C so that shouldn't be a problem for the moment. Once I get as much power as I can I'll see if I can dial back the fans a bit to reduce noise.


Currently the highest stable OC is 975 Core 1525 Mem. I haven't tried to adjust the mem any higher.
What exactly is a VRM? Afterburner doesn't have a temperature control for that so I said I'd stop fiddling until I know for sure.

BloodBath

Run the full test but even that isn't an indication of full stability. It's at least a good idea if you are close to stable. Only using the machine over a long period playing different games will prove how stable it is.

I'd expect it to be able to do 1000/1350 with stock voltage. Was the board power at +20%?

Instability is going to be caused by either temps or lack of voltage or board power.

I'm assuming the stock voltage is very low as the stock clocks are as low as you can get. Start putting more voltage into it. Your best bet is to manually put your fan speed to a constant 100% for testing, set your voltage to 1150mv and see how far you can get the core. Do not overclock the memory while you are testing the core.

The voltage is fine up to 1250mv. I'd say 1100 or so should be possible with 1150mv on the gpu. To get closer to 1200 you will need at least 1250mv and be able to keep it cool at that voltage.

Keep an eye on temps and try keep them below 70-75c.

VRM's are all the small chips that control voltage on the card.

Gbear

BloodBath wrote: »

Run the full test but even that isn't an indication of full stability. It's at least a good idea if you are close to stable. Only using the machine over a long period playing different games will prove how stable it is.

I'd expect it to be able to do 1000/1350 with stock voltage. Was the board power at +20%?

Instability is going to be caused by either temps or lack of voltage or board power.

I'm assuming the stock voltage is very low as the stock clocks are as low as you can get. Start putting more voltage into it. Your best bet is to manually put your fan speed to a constant 100% for testing, set your voltage to 1150mv and see how far you can get the core. Do not overclock the memory while you are testing the core.

The voltage is fine up to 1250mv. I'd say 1100 or so should be possible with 1150mv on the gpu. To get closer to 1200 you will need at least 1250mv and be able to keep it cool at that voltage.

Keep an eye on temps and try keep them below 70-75c.

VRM's are all the small chips that control voltage on the card.

Core Voltage was at 981mV by default.
There's a box with an option for "Force Constant Voltage".

Should that be ticked?

BloodBath

That's very low as I thought. No wonder it's not stable at 1000 core.

Don't enable that option. It will stop the voltage of the card dropping down when it's idle and drops it's clocks.

Gbear

There's a dropdown for Memory Voltage and Auxiliary voltage (1600 and 0 respectively).
I presume I'll leave them alone?

BloodBath

Don't touch anything except board power and gpu voltage. Adding more voltage to memory will only net small gains and more heat.

Gbear

The highest that Afterburner will let me OC the core is 1100.

The final stable OC I got to was 1100 - 1375. It was topping out at about 69C.

Any gains that I could get in the Memory would be marginal and it's fairly high temps so I'm happy enough with that.

Thanks for the help.

BloodBath

That's still around a 40% overclock on the core so you can't complain really.

BloodBath

You know you can unlock afterburner to go above 1100 as well right?

Gbear

BloodBath wrote: »

You know you can unlock afterburner to go above 1100 as well right?

It runs too hot anyway so I can't go much higher.

I actually had to dial it back to 1000MHz core and 1100mV.

It was on course to shoot up to 80C at 1100 1150.

BloodBath

I've dialed mine down a bit as well. The cooler gets a bit loud at 1200 1.3v in stressful games which means it's going to 70-80c. Back down to 1140@1.2v. It's a good cooler, my gpu just needs a bit too much voltage to be stable.