Just wanted to pass along a scaling analysis I've done on video card core overclocking. It's a follow-up to my findings on VRAM overclocking, which generated some interest here: http://forums.anandtech.com/showthread.php?t=2301435.
Enjoy and discuss!
Introduction
Test Bench: Intel i7-3770K@4.4GHz, Asus Maximus V Gene Motherboard, 16GB DDR3@1866MHz, NVidia GeForce Driver 314.22, AMD Catalyst Driver 13.4
In this test, we conduct overclocking scaling analysis on an EVGA GTX670 FTW and a Sapphire Radeon HD7870 OC. As it turns out, both of the video cards in this test have roughly the same amount of overclocking "headroom," about 15 percent, but that is entirely by chance. Even if you took a specific brand and model of video card, you could likely find up to 10 percent variability in overclocking headroom. Ultimately, that is not what this article is about - what we're looking at is what you get for each incremental increase in frequency. Our results can be roughly scaled up or down based on how lucky you are with your particular card.
For each of our video cards, we tested four different core frequencies, at intervals of exactly 5%. For our Nvidia card, we are referring to the "Boost" frequency, which is higher than the published core frequency. We carefully monitored this boost frequency during testing to make sure it remained constant (Nvidia's Boost feature can vary with temperature and load, which makes it somewhat difficult to benchmark). Note that for both cards, a VRAM overclock of approximately 15 percent was also applied, so as to minimize the extent to which memory bandwidth limited scaling of the core overclock. While both cards were factory-overclocked, we simply ignored those overclocks for purposes of our testing, using a baseline frequency at which reference GTX670 and HD7870 video cards would operate. One additional note - every benchmark below was tested three times to minimize the effects of test-to-test variability. We report the averaged results.
3DMark Fire Strike Performance Preset
Our first test is the recently-released 3dMark Fire Strike benchmark. We analyze only the Graphics Score, as the overall score is affected significantly by other components in the system, but here we're trying to isolate the video card as much as possible. This benchmark utilizes all of the latest DX11 features, and runs internally at 1920x1080, and is then scaled to the resolution being used on the test system.
Perhaps not surprisingly, the synthetic 3DMark Fire Strike benchmark shows some of the best overclocking results of all the benchmarks we ran, with a 12.1 percent boost on the GTX670 and an 8.7 percent boost on the HD7870. Also of note, the scaling curve is relatively linear, indicating that the core is likely the limiting factor in this test, especially given the pre-overclocked VRAM on our test cards.
Metro2033 Frontline Benchmark (1920x1080, 4x Anti-Aliasing, Maximum Settings, No Nvidia-Specific PhysX)
For our game tests, we'll go chronologically by age of the game, in case we see a pattern related to the vintage of the game engine being used in relation to core overclock scaling. Metro2033, released in March 2010, happens to be our most taxing benchmark, likely in part due to the inefficiency of its game engine. It uses very complex lighting, blur, and fog effects, but it's possible that its early DX11-based game engine was just slightly ahead of its time. There is no question that it is not the best looking game in this test, despite the strain it puts on our cards.
Metro2033's built-in benchmark demonstrated scaling that was starkly different from 3DMark. It was by far the worst of the six benchmarks we ran, with 6.1 percent faster performance on the GTX670 and 6.0 percent faster performance on the HD7870 when both are overclocked 15 percent. We previously found that this game responded very positively to VRAM overclocks, so our assumption is that the graphics engine is simply more bandwidth-contrained that the typical game engine.
Just Cause 2 Dark Tower Benchmark (1920x1080, Maximum Settings, 8x Anti-Aliasing, No Nvidia-Specific Water Effects)
Our next game test is Just Cause 2, which was also released in March of 2010. While it doesn't have quite the same number of effects as Metro2033, it arguably looks at least as good artistically. As opposed to Metro2033, Just Cause 2 is by far the least taxing of the game engines tested here.
Just Cause 2 illustrates the starkest example of how overclock scaling can vary from architecture to architecture. While the GTX670 runs 10.8 percent faster with a 15 percent overclock, the HD7870 only runs 5.1 percent faster. Interestingly, both cards demonstrate a stark plateau in overclock effectiveness, perhaps because the game engine is running into a bandwidth limitation caused by the 8xAA used in the test. Other than that graphical element, the graphics are the least demanding of all of the benchmarks in this article.
Continued below...
Enjoy and discuss!
Introduction
Test Bench: Intel i7-3770K@4.4GHz, Asus Maximus V Gene Motherboard, 16GB DDR3@1866MHz, NVidia GeForce Driver 314.22, AMD Catalyst Driver 13.4
In this test, we conduct overclocking scaling analysis on an EVGA GTX670 FTW and a Sapphire Radeon HD7870 OC. As it turns out, both of the video cards in this test have roughly the same amount of overclocking "headroom," about 15 percent, but that is entirely by chance. Even if you took a specific brand and model of video card, you could likely find up to 10 percent variability in overclocking headroom. Ultimately, that is not what this article is about - what we're looking at is what you get for each incremental increase in frequency. Our results can be roughly scaled up or down based on how lucky you are with your particular card.
For each of our video cards, we tested four different core frequencies, at intervals of exactly 5%. For our Nvidia card, we are referring to the "Boost" frequency, which is higher than the published core frequency. We carefully monitored this boost frequency during testing to make sure it remained constant (Nvidia's Boost feature can vary with temperature and load, which makes it somewhat difficult to benchmark). Note that for both cards, a VRAM overclock of approximately 15 percent was also applied, so as to minimize the extent to which memory bandwidth limited scaling of the core overclock. While both cards were factory-overclocked, we simply ignored those overclocks for purposes of our testing, using a baseline frequency at which reference GTX670 and HD7870 video cards would operate. One additional note - every benchmark below was tested three times to minimize the effects of test-to-test variability. We report the averaged results.
3DMark Fire Strike Performance Preset
Our first test is the recently-released 3dMark Fire Strike benchmark. We analyze only the Graphics Score, as the overall score is affected significantly by other components in the system, but here we're trying to isolate the video card as much as possible. This benchmark utilizes all of the latest DX11 features, and runs internally at 1920x1080, and is then scaled to the resolution being used on the test system.
Perhaps not surprisingly, the synthetic 3DMark Fire Strike benchmark shows some of the best overclocking results of all the benchmarks we ran, with a 12.1 percent boost on the GTX670 and an 8.7 percent boost on the HD7870. Also of note, the scaling curve is relatively linear, indicating that the core is likely the limiting factor in this test, especially given the pre-overclocked VRAM on our test cards.
Metro2033 Frontline Benchmark (1920x1080, 4x Anti-Aliasing, Maximum Settings, No Nvidia-Specific PhysX)
For our game tests, we'll go chronologically by age of the game, in case we see a pattern related to the vintage of the game engine being used in relation to core overclock scaling. Metro2033, released in March 2010, happens to be our most taxing benchmark, likely in part due to the inefficiency of its game engine. It uses very complex lighting, blur, and fog effects, but it's possible that its early DX11-based game engine was just slightly ahead of its time. There is no question that it is not the best looking game in this test, despite the strain it puts on our cards.
Metro2033's built-in benchmark demonstrated scaling that was starkly different from 3DMark. It was by far the worst of the six benchmarks we ran, with 6.1 percent faster performance on the GTX670 and 6.0 percent faster performance on the HD7870 when both are overclocked 15 percent. We previously found that this game responded very positively to VRAM overclocks, so our assumption is that the graphics engine is simply more bandwidth-contrained that the typical game engine.
Just Cause 2 Dark Tower Benchmark (1920x1080, Maximum Settings, 8x Anti-Aliasing, No Nvidia-Specific Water Effects)
Our next game test is Just Cause 2, which was also released in March of 2010. While it doesn't have quite the same number of effects as Metro2033, it arguably looks at least as good artistically. As opposed to Metro2033, Just Cause 2 is by far the least taxing of the game engines tested here.
Just Cause 2 illustrates the starkest example of how overclock scaling can vary from architecture to architecture. While the GTX670 runs 10.8 percent faster with a 15 percent overclock, the HD7870 only runs 5.1 percent faster. Interestingly, both cards demonstrate a stark plateau in overclock effectiveness, perhaps because the game engine is running into a bandwidth limitation caused by the 8xAA used in the test. Other than that graphical element, the graphics are the least demanding of all of the benchmarks in this article.
Continued below...
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