GeForce GT 640 DDR3 vs Radeon HD 3850 1GB

Intro

Compare that to the Radeon HD 3850 1GB, which features core clock speeds of 668 MHz on the GPU, and 828 MHz on the 1024 MB of GDDR3 RAM. It features 320(64x5) SPUs along with 16 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 3850 1GB		75 Watts
	Difference: 10 Watts (15%)

Memory Bandwidth

In theory, the GeForce GT 640 DDR3 should be a little bit faster than the Radeon HD 3850 1GB overall. (explain)

GeForce GT 640 DDR3		57024 MB/sec
Radeon HD 3850 1GB		52992 MB/sec
	Difference: 4032 (8%)

Texel Rate

The GeForce GT 640 DDR3 will be a lot (more or less 169%) more effective at texture filtering than the Radeon HD 3850 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3850 1GB		10688 Mtexels/sec
	Difference: 18112 (169%)

Pixel Rate

The GeForce GT 640 DDR3 is a lot (more or less 35%) more effective at full screen anti-aliasing than the Radeon HD 3850 1GB, and should be capable of handling higher resolutions without slowing down too much. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 3850 1GB		10688 Mpixels/sec
	Difference: 3712 (35%)

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 (counted in megabytes per second) that can be transferred past the external memory interface in a second. The number is calculated by multiplying the interface width by its memory clock speed. If the card has DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied per second. This is worked out by multiplying the total texture units by the core clock speed of the chip. The higher the texel rate, the better the 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 maximum amount of pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount 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 output rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.