GeForce GT 640 DDR3 vs Radeon HD 7950 3GB

Intro

Compare all of that to the Radeon HD 7950 3GB, which uses a 28 nm design. AMD has clocked the core frequency at 800 MHz. The GDDR5 RAM is set to run at a speed of 1250 MHz on this particular card. It features 1792 SPUs as well as 112 Texture Address Units and 32 ROPs.

Display Graphs

Hide Graphs

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 better than 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 will be a lot (about 211%) faster with regards to 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

If running with a high screen resolution is important to you, then the Radeon HD 7950 3GB is a better choice, by far. (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 max amount of information (counted in megabytes per second) that can be transported across the external memory interface within a second. It is worked out by multiplying the interface width by its memory speed. In the case of DDR memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better 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 can be applied in one second. This number is worked out 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 video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the most pixels the graphics card can 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 card's clock speed. ROPs (Raster Operations Pipelines - aka 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, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.