GeForce GT 640 DDR3 vs Radeon HD 3850 1GB

Intro

Compare all of that to the Radeon HD 3850 1GB, which has 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 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 3850 1GB		75 Watts
	Difference: 10 Watts (15%)

Memory Bandwidth

In theory, the GeForce GT 640 DDR3 should be a small 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 should be much (about 169%) more effective at anisotropic 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 quite a bit (approximately 35%) better at FSAA than the Radeon HD 3850 1GB, and able to handle higher screen resolutions better. (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 max amount of information (in units of megabytes per second) that can be moved across the external memory interface in one second. The number is worked out by multiplying the card's interface width by the speed of its memory. In the case of DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the 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 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 this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.