GeForce GT 640 DDR3 vs Radeon HD 7950 3GB

Intro

Compare those specifications to the Radeon HD 7950 3GB, which features GPU core speed of 800 MHz, and 3072 MB of GDDR5 memory running at 1250 MHz through a 384-bit bus. It also is comprised of 1792 Stream Processors, 112 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 7950 3GB		200 Watts
	Difference: 135 Watts (208%)

Memory Bandwidth

As far as performance goes, the Radeon HD 7950 3GB should in theory be much superior to the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 7950 3GB		240000 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 182976 (321%)

Texel Rate

The Radeon HD 7950 3GB should be a lot (approximately 211%) better at texture filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 7950 3GB		89600 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 60800 (211%)

Pixel Rate

The Radeon HD 7950 3GB should be much (approximately 78%) more effective at full screen anti-aliasing than the GeForce GT 640 DDR3, and also capable of handling higher resolutions while still performing well. (explain)

Radeon HD 7950 3GB		25600 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 11200 (78%)

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 largest amount of data (in units of megabytes per second) that can be moved past the external memory interface in a second. It is worked out by multiplying the card's bus width by its memory speed. If it uses DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

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

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