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Radeon HD 3870 1GB vs Radeon HD 4650 1GB

Intro

The Radeon HD 3870 1GB has a clock frequency of 775 MHz and a GDDR4 memory speed of 1125 MHz. It also uses a 256-bit memory bus, and uses a 55 nm design. It is comprised of 320(64x5) SPUs, 16 Texture Address Units, and 16 ROPs.

Compare those specs to the Radeon HD 4650 1GB, which features GPU clock speed of 600 MHz, and 1024 MB of GDDR3 memory set to run at 700 MHz through a 128-bit bus. It also is comprised of 320(64x5) SPUs, 32 Texture Address Units, and 8 ROPs.

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 1GB 55 Watts
Radeon HD 3870 1GB 106 Watts
Difference: 51 Watts (93%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 3870 1GB is 221% quicker than the Radeon HD 4650 1GB in general, because of its higher data rate. (explain)

Radeon HD 3870 1GB 72000 MB/sec
Radeon HD 4650 1GB 22400 MB/sec
Difference: 49600 (221%)

Texel Rate

The Radeon HD 4650 1GB should be a lot (approximately 55%) faster with regards to anisotropic filtering than the Radeon HD 3870 1GB. (explain)

Radeon HD 4650 1GB 19200 Mtexels/sec
Radeon HD 3870 1GB 12400 Mtexels/sec
Difference: 6800 (55%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 3870 1GB is superior to the Radeon HD 4650 1GB, and very much so. (explain)

Radeon HD 3870 1GB 12400 Mpixels/sec
Radeon HD 4650 1GB 4800 Mpixels/sec
Difference: 7600 (158%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

Price Comparison

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Radeon HD 3870 1GB

Amazon.com

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Radeon HD 4650 1GB

Amazon.com

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Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

Specifications

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Model Radeon HD 3870 1GB Radeon HD 4650 1GB
Manufacturer AMD AMD
Year Nov 19, 2007 Sep 10, 2008
Code Name RV670 XT RV730 PRO
Memory 1024 MB 1024 MB
Core Speed 775 MHz 600 MHz
Memory Speed 2250 MHz 1400 MHz
Power (Max TDP) 106 watts 55 watts
Bandwidth 72000 MB/sec 22400 MB/sec
Texel Rate 12400 Mtexels/sec 19200 Mtexels/sec
Pixel Rate 12400 Mpixels/sec 4800 Mpixels/sec
Unified Shaders 320(64x5) 320(64x5)
Texture Mapping Units 16 32
Render Output Units 16 8
Bus Type GDDR4 GDDR3
Bus Width 256-bit 128-bit
Fab Process 55 nm 55 nm
Transistors (Unknown) million 514 million
Bus PCIe 2.0 x16/AGP 8x PCIe 2.0 x16, AGP 8x
DirectX Version DirectX 10.1 DirectX 10.1
OpenGL Version OpenGL 3.0 OpenGL 3.0

Memory Bandwidth: Bandwidth is the max amount of information (counted in megabytes per second) that can be moved over the external memory interface in one second. It is worked out by multiplying the interface width by its memory clock speed. If it uses DDR memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This is calculated by multiplying the total number of texture units by the core clock speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the number of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.

Display Prices

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Radeon HD 3870 1GB

Amazon.com

Check prices at:

Radeon HD 4650 1GB

Amazon.com

Check prices at:

Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

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