GeForce GT 640 DDR3 vs Radeon HD 6770 1GB

Intro

Compare that to the Radeon HD 6770 1GB, which has a GPU core clock speed of 900 MHz, and 1024 MB of GDDR5 RAM running at 1050 MHz through a 128-bit bus. It also is comprised of 800 Stream Processors, 40 Texture Address Units, and 16 ROPs.

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

The Radeon HD 6770 1GB should theoretically be a small bit faster than the GeForce GT 640 DDR3 overall. (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 quite a bit (approximately 25%) faster with regards to 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 exactly the same pixel fill rate, so theoretically they should be equally good at at anti-aliasing, and be capable of handling the same screen 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 information (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 clock speed. If it uses DDR type memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed in one second. This number is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the 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 that the graphics chip could possibly write to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant 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.