GeForce GT 640 DDR3 vs Radeon HD 3870 512MB

Intro

Compare those specs to the Radeon HD 3870 512MB, which features a core clock frequency of 775 MHz and a GDDR3 memory frequency of 900 MHz. It also features a 256-bit memory bus, and uses a 55 nm design. It is comprised of 320(64x5) SPUs, 16 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 3870 512MB		106 Watts
	Difference: 41 Watts (63%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 3870 512MB is 1% faster than the GeForce GT 640 DDR3 overall, due to its greater bandwidth. (explain)

Radeon HD 3870 512MB		57600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 576 (1%)

Texel Rate

The GeForce GT 640 DDR3 will be a lot (more or less 132%) more effective at texture filtering than the Radeon HD 3870 512MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3870 512MB		12400 Mtexels/sec
	Difference: 16400 (132%)

Pixel Rate

If running with high levels of AA is important to you, then the GeForce GT 640 DDR3 is a better choice, but it probably won't make a huge difference. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 3870 512MB		12400 Mpixels/sec
	Difference: 2000 (16%)

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 largest amount of information (in units of megabytes per second) that can be moved across the external memory interface within a second. It's calculated by multiplying the interface width by its memory speed. If the card has DDR memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.