Overclocking my Sapphire 7950 Vapor-X

[hawk767]

I've had the card a couple months and am just started playing with overclocking it.

Right now I have it at 1150/1450 stable but each time I bump it to 1500 memory clock it crashes. So from here do I need to increase my voltage, the VDDC option in Trixx?

So far I've been running tests with the Heaven Benchmark on custom settings,

Quality: High
Tessellation: Normal
AA: x4
1920 x 1080
DX11

This is my first time toying with a gpu so I just want to be sure I don't fry something haha.

Temps have sat around mid 60's only jumping up to 66+ now that I've bumped by memory up to 1450. I'm curious as to what would be better to have raise higher now, the memory to that 1500 that I read of many people reaching or the core clock to 1200+.

 

[buildzoid]

The HD7950 has a 384 bit bus the memory is less important than core speed. Though if you want you could get after burner and use the VRAM voltage increase option to get a little more VRAM speed using 1.6-1.65v but it's riskier than pushing 1200mhz on the core using 1.2-1.3v because you can inflict permanent damage on the VRAM.

 

[hawk767]

The HD7950 has a 384 bit bus the memory is less important than core speed. Though if you want you could get after burner and use the VRAM voltage increase option to get a little more VRAM speed using 1.6-1.65v but it's riskier than pushing 1200mhz on the core using 1.2-1.3v because you can inflict permanent damage on the VRAM.

As far as I've read 1500 memory clock seems to be the max you can get on air so is the memory clock what is requiring a voltage jump or the core clock.

I used CCC's overdrive to set my power at +20% and the max volts I've seen is only 1.28 - 1.29 on GPU-Z and that's at 1400 memory clock. Will another bump of 50 really require that big of a voltage increase?

 

[buildzoid]

Send me a screenshot of GPU-z voltage readings. Because if that's voltage on the memory that it's reading then you have some really low power GDDR5 or GPU-z is reading it wrong as most cards have voltage between 1.5-1.6v on the VRAM at stock

 

[hawk767]

Send me a screenshot of GPU-z voltage readings. Because if that's voltage on the memory that it's reading then you have some really low power GDDR5 or GPU-z is reading it wrong as most cards have voltage between 1.5-1.6v on the VRAM at stock

Ok then I assume that the voltage is the MVDDC which reads a steady 1.602 V both idle and under load. I was thinking that the voltage was just the VDDC which under load is reading 1.238 as the max reading at 1150/1450. The only option available to change in trixx is the VDDC so I'll check out afterburner and see if that gives me anything.

 

[buildzoid]

Ok good. Set the MVDDC to 1.65v and no more. If it doesn't help put it back down to 1.6. So I if read right you're already pushing 1.3v on the core because that is about as far as I would push it. So if the MVDDC increase does nothing for mem clocks give up as 1200/1500mhz isn't much faster than 1150/1450.

 

[hawk767]

Now when I'm toying with Afterburner I'm able to change the voltage settings both core and memory.

Core Voltage: 1125
Memory Voltage: 1600

Now when I change the mV there is no voltage change on gpu-z it remains to show 1.602 instead of 1.625 which is what I try setting it to. I've read about this card being possibly volt locked or is it just the BIOs.

Edit: After a bit more toying with it all I think 1200/1400 is my max. I have my VDDC set to 1275 rather than 1300 and it ran fine on the tests I ran. I was able to bump my VDDC to 1300 and run my core up from 1210 - 1250 but the higher it got the more artifacts were showing up in Heaven Bench so I just dropped it back down.

These Heaven scores were all run with the same settings I showed in the beginning of the thread.

Windowed 1200/1400: 1402
Fullscreen 1200/1400: 1344
Fullscreen 1225/1400: 1354


The performance increase from the core after 1200 just isn't much unfortunately. My temps sat fine in the high 60's as well once I bumped the VDDC. 71 being max card temp and 73 being the VRM 1 and 2 temps.

The 1250/1400 test I stopped early because the artifacts were very noticeable.

I guess I can just overclock my cpu now at some point and to get further performance.

Edit 2: Running the Heaven Benchmark on Extreme,

Ultra Quality
Extreme Tessellation
8x AA

I managed a score of 887, max fps 77, min 14. So not bad I suppose. No crashes or problems so far but I'll see how long that holds while gaming.

I assume its just fine to keep it at normal boost settings, 950/1200 and bump it to my OC whenever I'm going to play a graphically intensive game?