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Radeon HD 4870: The Benefit Of CPU Overclocking

Do New Drivers Really Boost Performance?
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This is AMD’s fastest single-chip card with plenty of graphics processing muscle in reserve, which only come to light with a more powerful CPU. The following tables allow you to see how much performance the HD 4870 is able to bring to the screen with the additional processor frequency.

The driver versions and overclocked CPUs are listed directly after the chip name. The resolutions go from 1280x1024 to 1680x1050 to 1920x1200 pixels, first without anti-aliasing (0xAA), then in the same order with anti-aliasing (4xAA, and in Mass Effect 8xAA as well). The two upper lines of figures represent the frame rates, the lower line is the difference in performance in percentage.

Assassins Creed in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.8 57.7 58.4 57.9 44.4 43.5 43.8 305.7
HD 4870 (512 MB) CPU@3.47 66.1 65.9 64.7 50.7 48.6 47.3 343.3
Difference in performance in percentage 14.6 12.8 11.7 14.2 11.7 8.0 12.3

The additional 18.2 percent CPU speed is converted by the graphics card into as much as 14.6 percent higher frame rates. In the 1920 resolution, performance increase stops at 8 percent, although the HD 4870 would seemingly benefit from a clock rate of at least 4 GHz in Assassins Creed.

Call of Duty 4 in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.8 182.1 149.5 126.2 137.6 110.7 92.1 798.2
HD 4870 (512 MB) CPU@3.47 180.5 149.1 121.5 139.0 110.4 95.5 796.0
Difference in performance in percentage -0.9 -0.3 -3.7 1.0 -0.3 3.7 -0.3

Like the GeForce GTX 280, the Radeon HD 4870 shows no performance improvement with the additional CPU power in Call of Duty 4.

Crysis High in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.8 31.9 29.7 29.5 26.9 24.1 21.1 163.2
HD 4870 (512 MB) CPU@3.47 36.4 33.2 31.2 30.4 24.8 21.2 177.2
Difference in performance in percentage 14.1 11.8 5.8 13.0 2.9 0.5 8.6

Crysis gets a reasonable performance boost. The 18.2 percent jump in clock speed is visible in the 1280 resolution with 13 percent to 14 percent higher frame rates. At 1920 with anti-aliasing enabled, it’s all over—the HD 4870 runs out of steam. At 1680x1050 pixels (4xAA), it offers a minor increase of 3 percent.

Crysis Very High in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.8 28.8 22.0 18.1 22.0 15.7 11.4 118.0
HD 4870 (512 MB) CPU@3.47 31.3 21.0 17.6 21.3 15.1 11.5 117.8
Difference in performance in percentage 8.7 -4.5 -2.8 -3.2 -3.8 0.9 -0.2

With Very High image quality, the additional CPU performance only yields results at 1280. In other cases you must expect losses with this test system.

ET: Quake Wars in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.7 67.7 65.4 66.2 66.6 64.2 64.2 394.3
HD 4870 (512 MB) CPU@3.47 80.1 80.3 76.8 76.7 75.2 74.3 463.4
Difference in performance in percentage 18.3 22.8 16.0 15.2 17.1 15.7 17.5

The Catalyst 8.8 graphics driver doesn’t even start Quake Wars. Catalyst version 8.7 was used for the test. Results with 18.3 percent and 22.8 percent additional CPU performance would be intriguing, as only 18.2 percent was made available, and the results clearly show that the Radeon HD 4870 has much more potential in Quake Wars if it is combined with a more powerful CPU.

Half-Life 2 Episode 2 in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.8 107.2 101.4 100.6 105.8 101.5 100.1 616.6
HD 4870 (512 MB) CPU@3.47 120.2 113.0 112.5 117.6 112.8 109.1 685.2
Difference in performance in percentage 12.1 11.4 11.8 11.2 11.1 9.0 11.1

The results for Half-Life 2 Episode 2 are not surprising as the game is heavily dependent on the CPU. We suspect the HD 4870 could benefit from at least another 500 MHz of CPU clock speed before it reaches its limit.

Mass Effect in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
1280
8xAA
1680
8xAA
1920
8xAA
Overall
HD 4870 (512 MB) 8.8 95.9 92.2 81.9 63.9 48.4 38.8 62.1 47.1 37.5 567.8
HD 4870 (512 MB) CPU@3.47 104.5 100.1 83.3 64.5 48.8 38.8 62.3 47.1 37.7 587.1
Difference in performance in percentage 9.0 8.6 1.7 0.9 0.8 0.0 0.3 0.0 0.5 3.4

Without anti-aliasing, you can generate a few more frame at 1680x1050 pixels; above this the additional CPU power is ignored as the graphics card has reached its performance limit.

MS Flight Simulator X SP2 in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.8 25.2 25.9 25.9 25.9 25.8 25.7 154.4
HD 4870 (512 MB) CPU@3.47 29.3 28.6 28.5 29.7 28.0 28.9 173.0
Difference in performance in percentage 16.3 10.4 10.0 14.7 8.5 12.5 12.0

Flight Simulator X and the Radeon HD 4870 hungrily chew up the CPU overclocking and would happily take more before the graphics card would stop drawing the additional frames on screen. The limit is probably well over the 4 GHz CPU rate.

World in Conflict in fps 1280
0xAA
1680
0xAA
1920
0xAA
1280
4xAA
1680
4xAA
1920
4xAA
Overall
HD 4870 (512 MB) 8.8 48.0 49.9 47.5 43.9 37.0 33.8 260.1
HD 4870 (512 MB) CPU@3.47 52.9 54.1 50.9 44.6 37.6 32.4 272.5
Difference in performance in percentage 10.2 8.4 7.2 1.6 1.6 -4.1 4.8

Without anti-aliasing, the performance increase due to increased CPU clocking is perfectly fine, but with anti-aliasing, the gain is barely visible. The HD 4870 loses some frame rates in the 1920 resolutions, although 1 fps is within the measuring tolerances.

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