Overclocking, Testing Methodology and System Setup

Overclocking

Most everyone should know that NVIDIA makes overclocking your NVIDIA-based graphics card pretty easy with a very minor registry hack called “coolbits”.  Then, you can enter the driver and move some slider bars to reconfigure your core and memory frequencies without much effort. 

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BFG 7900 GT OC stock speeds

Our driver here shows the stock clock speeds of 475 MHz and 680 MHz (1360 MHZ DDR) are properly set.  But how far could I push the card and still get stable gaming results?

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Our top overclock for our sample card

Wow!  You can see that I was able to get the core to run at 550 MHz and the memory to run at nearly 750 MHz (1500 MHz DDR) without any corruption or instability.  These speeds are well over what even the BFG out-of-box overclock was set to.  Of course, BFG can’t guarantee every part will run at these speeds reliably, and that is why their overclocks are much more modest than what we found here.

In fact, there may be more reasons for a lower overclock that we are completely aware of due to some issues with the 7900 GTX cards from various vendors showing instability at their stock overclocked speeds. 

Testing Methodology

Graphics card testing has become the most hotly debated issue in the hardware enthusiast community recently.  Because of that, testing graphics cards has become a much more complicated process than it once was.  Where before you might have been able to rely on the output of a few synthetic, automatic benchmarks to make your video card purchase, that is just no longer the case.  Video cards now cost up to $500 and we want to make sure that we are giving the reader as much information as we can to aid you in your purchasing decision.  We know we can’t run every game or find every bug and error, but we try to do what we can to aid you, our reader, and the community as a whole.

With that in mind, all the benchmarks that you will see in this review are from games that we bought off the shelves just like you.  Of these games, there are two different styles of benchmarks that need to be described.

The first is the “timedemo-style” of benchmark.  Many of you may be familiar with this style from games like Quake III; a “demo” is recorded in the game and a set number of frames are saved in a file for playback.  When playing back the demo, the game engine then renders the frames as quickly as possible, which is why you will often see the “timedemo-style” of benchmarks playing back the game much more quickly than you would ever play the game.  In our benchmarks, the FarCry tests were done in this matter: we recorded four custom demos and then played them back on each card at each different resolution and quality setting.  Why does this matter?  Because in these tests where timedemos are used, the line graphs that show the frame rate at each second, each card may not end at the same time precisly because one card is able to play it back faster than the other — less time passes and thus the FRAPs application gets slightly fewer frame rates to plot.  However, the peaks and valleys and overall performance of each card is still maintained and we can make a judged comparison of the frame rates and performance.

The second type of benchmark you’ll see in this article are manual run throughs of a portion of a game.  This is where we sit at the game with a mouse in one hand, a keyboard under the other, and play the game to get a benchmark score.  This benchmark method makes the graphs and data easy to read, but adds another level of difficulty to the reviewer — making the manual run throughs repeatable and accurate.  I think we’ve accomplished this by choosing a section of each game that provides us with a clear cut path. We take three readings of each card and setting, average the scores, and present those to you.  While this means the benchmarks are not exact to the most minute detail, they are damn close and practicing with this method for many days has made it clear to me that while this method is time consuming, it is definitely a viable option for games without timedemo support.

The second graph is a bar graph that tells you the average framerate, the maximum framerate, and the minimum framerate.  The minimum and average are important numbers here as we want the minimum to be high enough to not affect our gaming experience.  While it will be the decision of each individual gamer what is the lowest they will allow, comparing the Min FPS to the line graph and seeing how often this minimum occurs, should give you a good idea of what your gaming experience will be like with this game, and that video card on that resolution.

Our tests are completely based around the second type of benchmark method mentioned above — the manual run through.

Test System Setup

For this review we are comparing the BFG 7900 GT OC model and BFG 7900 GT OC SLI against the reference 7900 GT scores.  I also threw in the ATI X1800 XT graphics card that is currently selling for about the same price as the 7900 GT models.  Keep in mind that the 7900 GT only has 256 MB of on-board video memory while the X1800 XT has 512 MB — this could make for some interesting testing results. 

For a detailed comparison of the 7900 GT to other GPUs, see our 7900 GT review.

Test System Setup

GPUs

BFG 7900 GT OC (475/680)
Reference 7900 GT (450/650) – Review
ATI X1800 XTReview

Processor

Athlon X2 4800+ – Review

Motherboard

Asus A8N32-SLI DeluxeReview

Chipset Driver

6.85

Memory

2 x 1 GB Corsair XMS3500LL Pro

Memory Timings

6-2-3-2.0

Sound Card

Sound Blaster Audigy 2 Value

Hard Drive

Western Digital SE16 400 GB

Operating System

Windows XP Professional SP1

GPU Driver

84.21

Power Supply

Silverstone Zeus 650 watt (quad 12V rails)

Software tested:

  • Guild Wars
  • Far Cry
  • Battlefield 2
  • FEAR
  • Call of Duty 2
  • Half-Life 2
  • Half-Life 2: Lost Coast
  • 3DMark06
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