GeForce GT 640 DDR3 vs Radeon HD 3870 1GB

Intro

Compare all of that to the Radeon HD 3870 1GB, which comes with clock speeds of 775 MHz on the GPU, and 1125 MHz on the 1024 MB of GDDR4 memory. It features 320(64x5) SPUs as well as 16 TAUs and 16 Rasterization Operator Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 3870 1GB		106 Watts
	Difference: 41 Watts (63%)

Memory Bandwidth

As far as performance goes, the Radeon HD 3870 1GB should theoretically be much superior to the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 3870 1GB		72000 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 14976 (26%)

Texel Rate

The GeForce GT 640 DDR3 should be quite a bit (more or less 132%) faster with regards to anisotropic filtering than the Radeon HD 3870 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3870 1GB		12400 Mtexels/sec
	Difference: 16400 (132%)

Pixel Rate

If using a high screen resolution is important to you, then the GeForce GT 640 DDR3 is the winner, not by a very large margin though. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 3870 1GB		12400 Mpixels/sec
	Difference: 2000 (16%)

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

Specifications

Memory Bandwidth: Memory bandwidth is the max amount of data (measured in MB per second) that can be moved over the external memory interface within a second. The number is worked out by multiplying the card's bus width by its memory clock speed. If the card has DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly record to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.