GeForce GT 640 DDR3 vs Radeon HD 4850 2GB

Intro

Compare those specs to the Radeon HD 4850 2GB, which features core clock speeds of 625 MHz on the GPU, and 993 MHz on the 2048 MB of GDDR4 RAM. It features 800(160x5) SPUs as well as 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 4850 2GB		110 Watts
	Difference: 45 Watts (69%)

Memory Bandwidth

The Radeon HD 4850 2GB should in theory perform a little bit faster than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4850 2GB		63552 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 6528 (11%)

Texel Rate

The GeForce GT 640 DDR3 should be a little bit (approximately 15%) faster with regards to texture filtering than the Radeon HD 4850 2GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4850 2GB		25000 Mtexels/sec
	Difference: 3800 (15%)

Pixel Rate

The GeForce GT 640 DDR3 is quite a bit (about 44%) more effective at FSAA than the Radeon HD 4850 2GB, and also will be able to handle higher resolutions without slowing down too much. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4850 2GB		10000 Mpixels/sec
	Difference: 4400 (44%)

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 data (in units of megabytes per second) that can be transferred past the external memory interface within a second. It's calculated by multiplying the card's bus width by its memory clock speed. In the case of DDR type RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card can possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.