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

Nvidia has released its long awaited GeForce GTX 680 based on its brand new Kepler DX11.1 GK104 architecture two weeks ago.  On release day, we brought you Part One of our GTX 680 series, Nvidia’s GTX 680 arrives!  “Faster, Smoother, Richer” – is it enough to take the Performance Crown?    We found that the GTX 680 beats the HD 7970 in every metric including performance – and it is priced $50 less.

We now have had two more weeks hand’s on experience testing the GTX 680 versus the HD 7970 and we have learned quite a bit more that we would like to share with you.  In Part One, we learned that the GTX 680 does indeed overclock.   We were able to get it stably up from its stock base clocks (1006/3004MHz) to a decent overclock (1156/3029MHz) which compared favorably with our overclock of the HD from stock (925/1375MHz) to overclocked (1100/1400MHz).  However, we did not adjust the voltage nor the fan speed,  nor did we find our maximum overclock for each card’s memory.

For Part Two, we will compare the performance of our overclocked GTX 680 to our overclocked HD 7970 as a starting point as we overclock each of them to the edge of stability by maxing out the voltage and fan speed to give you an idea of what future Super Overclocked versions of each of these cards may be like and how they may related to each other in terms of performance as faster and faster overclocked versions of each card appear.

In Part One, we compared the relative performance of the GTX 680, GTX 580 and GTX 690, as well as the HD 7970, HD 6970 and HD 6990.  The dual-GPU cards of the last generation were generally faster although overclocked, the GTX 680 and the HD 7970 approached their performance in some games.  The HD 6970 and to a lesser extent, the GTX 580 were left in the dust.  This time, we will only be comparing the  HD 7970 to the GTX 680 and we shall overclock them each as far as we can.  This time we shall adjust the voltage as far as it is useful and as far as our overclocking tools – MSI’s Afterburner for Radeon and EVGA’s Precision X for GeForce – will allow us.

We are also going to revisit the “Power Usage” section as befits overclocking in this review.  We noticed that the HD 7970 drew about 44W more than the GTX 680 when both were overclocked without any voltage adjustment and we look forward to seeing what happens to each cards’ power requirements when the clocks go up with additional voltage.

AMD has already launched most of its 28nm DX11.1 series – $550 for their flagship single-GPU HD 7970  – as well as their HD 7950, HD 7870 and HD 7850, down to their entry-level enthusiast HD 7770 and HD 7750 cards. To compete, Nvidia has launched its new Kepler architecture 28nm DX11.1 GeForce lineup with its GTX 680 flagship heralding the rest of the series as forthcoming. The reference GTX 680 is an overall better value than the reference HD 7970 as it comes with a MSRP of $499 which is $50 less than the slower HD 7970. However, we still need to answer the question: Is an overclocked HD 7970 worth the $50 premium over the GTX 680?

That question is important because we expect that Nvidia will shortly launch it’s own entire 28nm DX11.1 line-up based on their GK104 “Kepler” architecture.  We expect to see the GTX 670 and GTX 660 as well as the GTX 550 launch within a few months and we need to see what this new 28nm Kepler architecture brings over their GF110/100 series besides DX11.1 and a smaller process. Overclocking our GTX 680 to its maximum may give us some idea of future GK104 core scalability as Nvidia refines their process.  And we shall get an idea if AMD’s “Tahiti” architecture will be able to scale enough for highly overclocked versions of the HD 7970 to catch up to the GTX 680.  AMD is loathe to drop pricing on the HD 7970 as it would cause a cascade effect on their entire line up which has been premium-priced over the last generation.

To properly bring you this review, we purchased a PowerColor HD 7970 from NewEgg and put it through its paces with the very latest AMD performance drivers – Catalyst 12-3 which is even newer that the set we tested for the GTX 680 launch.  We are also using the very latest WHQL GeForce drivers 300.10 which is an upgrade over the launch drivers but appears to have no performance differences in our games.

Today you will see us pit our PowerColor HD 7970, which is now further overclocked from 1100/1400MHz to 1200/1575MHz, against the new GTX 680 which is further overclocked from 1156/3029MHz to 1181/3604MHz.   Sometimes it is a bit confusing when talking about the GTX 680’s “stock” clocks because there is a dynamic GPU Boost which further automatically increases the clocks by +50MHz to +100MHz over the ‘base clock’ of 1006/3004MHz  There is another way to look at it; we ultimately boosted the GTX 680’s clocks by +175MHz on the core and +600MHz on the memory while we boosted the HD 7970’s clocks by +275MHz on the core and +200MHz (+400MHz, the way Nvidia reports it) on the memory clocks.

We continue to benchmark with 21 modern games and with 3 synthetic benchmark at 1920×1200 and 2560×1600 resolutions and with details fully maxed and with 4x or 8xAA/16xAF applied whenever possible.

Is the overclocked HD 7970 worth $50 more than its rival, Nvidia’s GTX 680?

We declared the GTX 680 the performance winner and could find nothing compelling to recommend the HD 7970 at fifty dollars more, two weeks ago.  We believe that AMD is immediately going to respond to Nvidia’s GTX 680 launch by allowing their partners to overclock the current HD 7970 and we expect to see super-overclocked “halo” cards, appear at the tech sites so as to give the impression that the HD 7970 is not so far behind the GTX 680.  One of these such cards is the Sapphire “Toxic” HD 7970 and it is expected to be clocked at 1150/1500MHz.  Since our own PowerColor HD 7970 can supass this overclock (1200/1575MHz), we believe that we have a very fair representation of what is coming in the near future for our evaluation today.

Widespread e-tail availability of the GeForce GTX 680 has not happened yet. So one still has a little time to decide what to do and this review is designed to help with an important potential upgrade.  Since we do not want any chance of our CPU “bottlenecking” our graphics, we continue testing both of our graphics cards with our Intel Core i7-920 at 4.20GHz (approximately the same performance as a mildly overclocked Core i7-2700K), 6 GB Kingston DDR3 using a Gigabyte X58 16x + 16x PCIe CrossFire/SLI motherboard.

Before we take a look at overclocking and power draw, let’s check out the testing platform.