The GTX 680 Arrives! – Part Two, Maximum Overclocking vs. the HD 7970

Overclocking, Power Draw & Temperatures

In our charts we use the memory clocks as Nvidia and AMD each express them.  You can multiply the AMD clocks by 2X to get the equivalent data rates if you wish; or cut the Nvidia clocks in half.  At any rate, Nvidia has actually clocked its card’s memory much higher than AMD’s.

Here are the settings (base clocks before GPU Boost are used for the GTX 680):

GTX 680 (1006/3004MHz  stock)

1156/3029MHz   >>>  1181/3579MHz) – 1181/3604MHz

HD 7970 (925/1375MHz stock)

1100/1400MHz  >>> 1125/1575MHz  >>> 1200/1575MHz

This evaluation is based on overclocking each card in three steps as far as they will go; first at stock and then with a substantial core overclock, followed by a memory overclock which is finally followed by a voltage increase.  This appears to be representative of each card’s performance  scaling by overclocking these cards.

Each of our competing video cards was overclocked as far as it could go without exceeding the core voltage or thermals so as to throttle the respective GPUs.  We got 100% stability from each of our GPUs at the noise-expense of running their cooling fans each at 85%.

We used MSI’s Afterburner to overclock our PowerColor HD 7970 and EVGA’s Precision X for our GTX 680.  Both utilities allowed for quite a bit of control over each card’s overclock and we were also able to adjust the voltage.  Overclocking the GTX 680 beyond the stock overclock was easy. No one should let the boost clocks intimidate them. Using EVGA Precision tool, simply push the sliders to the right as far as you dare and set the clocks.  We finally settled on +175MHz on the core and 600MHz on the core.

We did exactly the same thing with our PowerColor HD 7970. Its stock clocks are 925/1375 and we pushed them beyond the fastest AMD partner-overclocked Radeon HD 7970’s clocks to 1200MHz/1575MHz.

We always use EVGA’s Precision overclocking tool for Nvidia cards. They recently added integrated GPU voltage adjustments. In addition to the EVGA GeForce GTX 680, EVGA has also introduced a new version of its popular “Precision” overclocking software, EVGA Precision X. It allows you to fine tune your GeForce graphics card, including GPU Clock speed, GPU Voltage, Memory Clock speed and Fan speed.

EVGA Precision X features many new and key features:

• · Brand New GUI – Built from the ground up for the next generation of graphics accelerators.
• · Advanced Hardware Monitoring – See GPU vitals in real time.
• · In Game Monitoring – See your GPU vitals, without leaving your game.
• · Frame Rate Target – GeForce GTX 680 will adjust power/clock dynamically to match set framerate.
• · Fan Curve – Setup and advanced fan profile.

Learn More about EVGA Precision X

Temperature

Our ambient (room temperatures) were fairly warm – 74-78F – so as to approximate a warm Spring day. Be aware that we used our Thermaltake Element G case which has excellent airflow for an oversized midtower. The GTX 680 runs quite cool at even our first mild overclock, in the low to mid-50s C even under load. However, once the core speed increased, so did the temperatures until we were idling in the low 60s when we hit near the 1300MHz peak on the core from boost and temperatures would rise into the low-80sC.  In comparison, the PowerColor HD 7970 tolerated higher temperatures into the low 90sC.

You can see from the performance charts what effects increasing the core speed has on the GTX 680 – from the reference speed of 1006/3006MHz , past adding +150MHz to finally settling on +175MHz.

Power Draw

We did a rough comparison by using our entire system running identical stressful benchmarks while monitoring with Kill-A-Watt. Previously, our GTX 680 drew 195W at idle before any voltage adjustments.  Here is the GTX 680 in our system at idle when it is fully overclocked with the maximum voltage boost.  It uses ten watts more power at idle when overclocked.

Now we ran our benches continually and looked for the peak usage of power with our GTX 680 overclocked as far as it would go stably with the fan at 85% and with the maximum voltage increase. At stcock, the absolute peak power usage was a blip at 451W. Now let’s see how far the total systen power draw increases when we overclock and overvolt our GTX 680.

Our system draws 44W more with the overclocked/overvolted GTX 680 over the stock GTX 680 – the very same amount that the HD 7970 draws on the stock fan profile and stock voltage.  Now let’s crank up the voltage of the HD 7970 and fan to 85% and see how far over 495W it climbs.

HD 7970 OC & Overvolt Maximum Power Draw

The PowerColor HD 7970 when overclocked and overvolted draws 102W more than overclocked on the stock fan profile and with the stock voltage.  It also uses over 100W more than the GTX 680 in the same situation and in the same system!

Noise

Both cards are extraordinarily quiet for high-end flagship cards. It appears that Nvidia has especially tuned the GTX 680 to be quiet somewhat at the expense of cooling. It will be interesting to see what cooling designs their partners implement.  However, when a fan is turned up to 85% it becomes annoying.  The GTX 680 might be a little quieter than the PowerColor HD 7970 but it is subjective and neither are ideal over 60%.  We use 85% to keep the cards cool and stable only for benches.  When we play games for ourself, we move the clocks to maximum for the stock voltage and fan profile.

Let’s head to our performance charts to see how the Super Overclocked HD 7970 fairs against a highly overclocked reference GTX 680 and peer a bit into the future performance of these cards.