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How Well Did We Do?
After loads of tests (and modding the fan to run at a much higher speed), we finally pegged the maximum stable clock speeds of our Radeon HD 4870 at 855 MHz GPU and 1200 MHz RAM. That's a 105 MHz (14%) overclock of the GPU and an amazing 300 MHz (33%) overclock of its GDDR5 memory. That gives our Radeon HD 4870 a significant boost in fillrate and an incredible memory bandwidth of 153.6 GB/s!
Let's take a look at how the overclocked Radeon HD 4870 compares to the stock Radeon HD 4870 and a selection of other cards.
|
Overclocked |
Radeon HD 4870 |
GeForce |
GeForce |
GeForce |
Core Speed |
855 MHz |
750 MHz |
576 MHz |
738 MHz |
675 MHz |
Texture Fill Rate |
34,200 MTexels/s |
30,000 MTexels/s |
36,864 MTexels/s |
47,232 MTexels/s |
43,200 MTexels/s |
Pixel Fill Rate |
13,680 MPixels/s |
12,000 MPixels/s |
16,128 MPixels/s |
11,808 MPixels/s |
10,400 MPixels/s |
Memory
Bus |
256-bits |
256-bits |
448-bits |
256-bits |
256-bits |
Memory |
GDDR5 |
GDDR5 |
GDDR3 |
GDDR3 |
GDDR3 |
Memory Speed |
1100 MHz |
900 MHz |
999 MHz |
1100 MHz |
1100 MHz |
Memory |
153.60 GB/s |
115.20 GB/s |
111.89 GB/s |
70.40 GB/s |
70.40 GB/s |
With its memory clock boosted to 1200 MHz, the overclocked Radeon HD 4870 has more than twice the memory bandwidth of the GeForce 9800 GTX+ and the GeForce 8800 GTS 512MB. That sure is a WHOLE LOT of memory bandwidth!
On the other hand, the GPU overclock of 105 MHz raised its fillrate to just over 34 gigatexels/s. That is about 27.6% lower than that of the GeForce 9800 GTX+.
Alright, let's give the overclocked Radeon HD 4870 a spin and see how well it does against the standard Radeon HD 4870, and a selection of other graphics cards. We will also examine which is more important - fillrate or memory bandwidth.
Testing The Overclocked Radeon HD 4870
Testbed
Processor |
Intel Core 2 Extreme QX9650 |
|
Motherboard |
ASUS P5B-E Plus |
|
Memory |
Two G.Skill 1GB PC2-6400 DDR2 memory modules |
|
Graphics Card |
ATI Radeon HD 4870 |
|
Hard Drives |
120GB Seagate Barracuda 7200.9 SATA hard drive |
|
Operating System |
||
Power Supply |
Mushkin 580W PSU |
The Graphics Cards
Graphics Card |
Core Clock |
Memory Clock |
Memory Bus Width |
Driver |
ATI Radeon HD 4870 |
855 MHz |
1200 MHz |
256-bits |
ATI Catalyst 8.7 |
NVIDIA GeForce GTX 260 |
576 MHz |
999 MHz |
256-bits |
NVIDIA ForceWare 177.39 |
NVIDIA GeForce 9800 GTX+ |
738 MHz |
1100 MHz |
256-bits |
NVIDIA ForceWare 177.39 |
NVIDIA GeForce 9800 GTX |
675 MHz |
1100 MHz |
256-bits |
NVIDIA ForceWare 177.39 |
NVIDIA GeForce 8800 GTS 512MB |
650 MHz |
972 MHz |
256-bits |
NVIDIA ForceWare 175.19 |
ATI Radeon HD 3870 |
775 MHz |
1125 MHz |
256-bits |
ATI Catalyst 8.7 |
ATI Radeon HD 3850 |
668 MHz |
828 MHz |
256-bits |
ATI Catalyst 8.7 |
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