GeForce GT 640 DDR3 vs Radeon HD 4890 2GB

Intro

Compare that to the Radeon HD 4890 2GB, which comes with core clock speeds of 1000 MHz on the GPU, and 975 MHz on the 2048 MB of GDDR5 RAM. It features 800(160x5) 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 4890 2GB		190 Watts
	Difference: 125 Watts (192%)

Memory Bandwidth

The Radeon HD 4890 2GB should in theory perform a lot faster than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4890 2GB		124800 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 67776 (119%)

Texel Rate

The Radeon HD 4890 2GB should be much (about 39%) better at texture filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 11200 (39%)

Pixel Rate

The Radeon HD 4890 2GB should be just a bit (more or less 11%) faster with regards to AA than the GeForce GT 640 DDR3, and also will be capable of handling higher resolutions while still performing well. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 1600 (11%)

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 maximum amount of information (measured in MB per second) that can be moved across the external memory interface in a second. It is calculated by multiplying the card's 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 memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels the video card can possibly write to the local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the number of Render Output Units by the the core 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 output rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.