GeForce GT 640 DDR3 vs Radeon HD 3850 256MB

Intro

Compare those specs to the Radeon HD 3850 256MB, which features core clock speeds of 668 MHz on the GPU, and 828 MHz on the 256 MB of GDDR3 RAM. It features 320(64x5) SPUs as well as 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 256MB		75 Watts
	Difference: 10 Watts (15%)

Memory Bandwidth

Performance-wise, the GeForce GT 640 DDR3 should in theory be a little bit better than the Radeon HD 3850 256MB overall. (explain)

GeForce GT 640 DDR3		57024 MB/sec
Radeon HD 3850 256MB		52992 MB/sec
	Difference: 4032 (8%)

Texel Rate

The GeForce GT 640 DDR3 should be a lot (approximately 169%) more effective at AF than the Radeon HD 3850 256MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3850 256MB		10688 Mtexels/sec
	Difference: 18112 (169%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is a better choice, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 3850 256MB		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: Memory bandwidth is the maximum amount of information (measured in MB per second) that can be transferred across the external memory interface in one second. It's worked out by multiplying the interface width by its memory speed. If it uses DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This number is calculated by multiplying the total texture units of the card by the core speed of the chip. The higher 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 maximum amount of pixels the graphics card can possibly record to the local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.