GeForce GT 640 DDR3 vs Radeon HD 6770 1GB

Intro

Compare that to the Radeon HD 6770 1GB, which features clock speeds of 900 MHz on the GPU, and 1050 MHz on the 1024 MB of GDDR5 RAM. It features 800 SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 6770 1GB		108 Watts
	Difference: 43 Watts (66%)

Memory Bandwidth

As far as performance goes, the Radeon HD 6770 1GB should in theory be a small bit better than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 6770 1GB		67200 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 10176 (18%)

Texel Rate

The Radeon HD 6770 1GB will be a lot (more or less 25%) more effective at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 6770 1GB		36000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 7200 (25%)

Pixel Rate

Both cards have the exact same pixel fill rate, so in theory they should perform equally good at at AA, and be capable of handling the same resolutions. (explain)

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: Bandwidth is the largest amount of data (measured in megabytes per second) that can be transported past the external memory interface within a second. It's calculated by multiplying the card's interface width by its memory clock speed. If it uses DDR type RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card can possibly record to its local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.