Weird 7950 overclock

[Alex780]

Hi everyone!

 

I've been trying to get a good overclock out of my MSI HD 7950 Twin Frozr recently and I got clocks of 1100 MHz core and 1700 MHz memory at stock voltage (1188 mV core and 1550 mV memory).

I thought I could probably go higher on the core so I tried overclocking it with a Vcore increase. But what's weird is that I couldn't get a stable overclock even at 1150 MHz (which is only 50 MHz more!) with a 1300 mV Vcore! I tried different combinations of voltage increases and core clock increases and all the stability tests were failed. Basically, increasing the Vcore didn't help overclocking at all.

Have you experienced such a thing already? I'm curious to know whether it's something that can happen sometimes or there is just something wrong. I am using Msi afterburner.

 

By the way, I have bypassed the drivers overdrive limits thanks to this short guide http://forums.guru3d.com/showthread.php?t=359671 and made sure that the Vcore was increased as demanded by reading its value on the afterburner built-in hardware monitor (I checked "unlock voltage monitoring").

 

Thanks for your replies!

[Bluejay0]

50Mhz is still alot when overclocking. 

[Sarcasm]

50MHz on a GPU isn't remotely close to 50MHz on a CPU. If you can't push it past that point, you simply lost the silicon lottery.

[Levent]

yup it happens with my Sapphire HD7850 OC too

1100Mhz 1.14v stable but i cant get to 1150mhz with 1.22v ,BUT my other msi card does 1300mhz with that voltage.

[Alex780]

I still managed to get a 140/450 MHz overclock though

[maazster]

Thats a great overclock, don't forget the silicon lottery.

[ericlee30]

No doubt, even if you can not get it stable at 1150 on the core clock, that is a really good overclock. Like some have said "silicon lottery" is key. For an example I have 3 7950's in my main rig, and my XFX 7950 black edition overclocks to 1200 on the core clock and 1725 on the memory clock stable at 1.3V.

[TechFan@ic]

Run GPU-Z, go to the sensors tab, look for "VDDC" see if it actually changes to 1.3v.
Use "Force Constant Voltage" in MSI afterburner to see the change in real-time.

[Alex780]

It might come from the method I used to bypass overdrive limits. I found this http://forums.anandtech.com/showthread.php?t=2263110 and they say it is more stable. I wonder if it's really going to change my oc results. I doubt so to be honest but I'll give it a shot.

[Alex780]

Update: It didn't change my overclock results but corrected some screen flickering while using afterburner. It simply looks like a lost the silicon lottery. 

[Alex780]

Run GPU-Z, go to the sensors tab, look for "VDDC" see if it actually changes to 1.3v.

Use "Force Constant Voltage" in MSI afterburner to see the change in real-time.

 

In GPU-Z, my Vcore never reaches the value set in afterburner. When I increase it, I see an increase in GPU-Z though and my core temps are affected too. But when I check "Force constant voltage" it doesn't lock the Vcore. I see its value fluctuate as it did before.

[TechFan@ic]

In GPU-Z, my Vcore never reaches the value set in afterburner. When I increase it, I see an increase in GPU-Z though and my core temps are affected too. But when I check "Force constant voltage" it doesn't lock the Vcore. I see its value fluctuate as it did before.

It will fluctuate while you're at the desktop, force constant voltage, run a benchmark or play a game for a few seconds, then alt-tab back into the desktop and check for the highest value.

I witnessed this fluctuation at the desktop as well, however when I play a game the voltage values become constant.

[Alex780]

It will fluctuate while you're at the desktop, force constant voltage, run a benchmark or play a game for a few seconds, then alt-tab back into the desktop and check for the highest value.

I witnessed this fluctuation at the desktop as well, however when I play a game the voltage values become constant.

 

The fluctuations occur even while stress testing (Kombustor or OCCT). Looks like there is something wrong between afterburner and my gpu...

Sorry not to have mentioned it in the first place.

[TechFan@ic]

The fluctuations occur even while stress testing (Kombustor or OCCT). Looks like there is something wrong between afterburner and my gpu...

Sorry not to have mentioned it in the first place.

Try an actual game, I tested this on Crysis 3.