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Analysis: Overclocking

Radeon HD 5770, Radeon HD 4890, And GeForce GTX 275 Overclocked
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The individual results, as well as the impact of the various clock speed settings, are covered individually in the sections for each graphics card. Here we want to try and summarize the most important conclusions from the benchmarks.

It'd seem that the results are clear. Overclocking sometimes allows your graphics card to reach the performance of the next highest class of GPU. At default speeds, MSI’s GeForce GTX 275 Lightning was only one or two percent shy of the GeForce GTX 285. However, once it was overclocked, the MSI card had no trouble beating the GTX 285 at stock speeds. Just bear in mind that you'll also pay more for overclocked versions of the most aggressive cards, so before you buy, make sure you aren't indeed paying for the higher-class card, too.

There is no faster graphics chip in the Radeon HD 4800-series to which we could compare the Radeon HD 4890. The performance boost from overclocking is almost twice that of the Nvidia card though, demonstrating this card’s potential. The following table shows the overall score (in FPS) for the reference cards and our test candidates.


Cumulative FPS
MSI N275GTX Lightning Max OC (GTX 275 1,792MB)1,838.5
GeForce GTX 285 (1,024MB)1,795.0
MSI N275GTX Lightning (GTX 275 1,792MB)1,769.1
MSI R4890 Cyclone SOC Max OC (HD 4890 1,024MB)1,750.6
MSI N275GTX Lightning No OC (GTX 275 1,792MB)1,694.4
MSI R4890 Cyclone SOC (HD 4890 1,024MB)1,689.6
GeForce GTX 275 (896MB)1,677.1
MSI R4890 Cyclone SOC No OC (HD 4890 1,024MB)1,543.4
Radeon HD 4890 (1,024MB)1,523.6
ATI Radeon HD 5770 OC (1,024MB)1,433.5
ATI Radeon HD 5770 (1,024MB)1,332.9
Radeon HD 4870 (512MB)1,327.1


Aside from the higher default clock speeds, is there any incentive for buyers to choose an OC Edition over a normal card? MSI’s GeForce GTX 275 certainly has some advantages compared to the reference design. For one thing, its cooler is more effective, while also running quieter. MSI’s OC Edition of the GeForce GTX 275 never exceeded 42 dB(A), even set to its highest overclocked speed, whereas Nvidia's reference cooler reached 44.2 dB(A). Thanks to MSI’s optimized cooler design, heat was also not an issue, reaching a mere 76 to 78 degrees Celsius under load, while Nvidia’s reference design struggled to keep the GPU at 92 degrees. In short, this card offers better performance than the reference design while still running cooler and quieter.

Things are a little different where MSI’s Radeon HD 4890 is concerned. Although its huge cooler can handle the higher clock speeds and resulting greater heat output, it does get louder than the reference model when running at full blast. Also, power consumption skyrockets when the card is overclocked. Our system’s power consumption jumped from 312 watts using the stock Radeon HD 4890 to a sobering 390 watts with the overclocked OC Edition. Thus, the GTX 275 OC Edition wins in a direct comparison, since it achieves a better cumulative frame rate, produces less noise, and stays cooler.

Below you’ll find one final chart that ranks the cards' efficiency. We take the cumulative frame rate (in FPS) and divide it by the system power to determine how many frames we get per watt. As you can see, the Radeon HD 5770 is the clear winner here. Also of note is that the overclocked cards score better than their siblings running at reference clock speeds.

Graphics Card and Chip Class
FPS
Watts
FPS per Watt
ATI Radeon HD 5770 OC (1,024MB)1,433.52316.21
ATI Radeon HD 5770 (1,024MB)1,332.92255.92
MSI N275GTX Lightning (GTX 275 1,792MB)1,769.13325.33
MSI N275GTX Lightning Max OC (GTX 275 1,792MB)1,838.53505.25
MSI N275GTX Lightning No OC (GTX 275 1,792MB)1,694.43255.21
GeForce GTX 285 (1,024MB)1,795.03485.16
Radeon HD 4890 (1,024MB)1,523.63124.88
Radeon HD 4770 (512MB)971.61994.88
GeForce GTX 275 (896MB)1,677.13514.78
Radeon HD 4870 (512MB)1,327.12884.61
MSI R4890 Cyclone SOC Max OC (HD 4890 1,024MB)1,750.63904.49
MSI R4890 Cyclone SOC (HD 4890 1,024MB)1,689.63804.45
MSI R4890 Cyclone SOC No OC (HD 4890 1,024MB)1,543.43484.44

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