GeForce GT 640 DDR3 vs Radeon HD 3870 512MB

Intro

Compare all of that to the Radeon HD 3870 512MB, which comes with GPU core speed of 775 MHz, and 512 MB of GDDR3 memory set to run at 900 MHz through a 256-bit bus. It also is comprised of 320(64x5) SPUs, 16 TAUs, 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

As far as performance goes, the Radeon HD 3870 512MB should theoretically be just a bit better than the GeForce GT 640 DDR3 in general. (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 is a lot (approximately 132%) better at anisotropic 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

The GeForce GT 640 DDR3 will be a bit (more or less 16%) better at AA than the Radeon HD 3870 512MB, and able to handle higher screen resolutions better. (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 max amount of data (in units of megabytes per second) that can be moved past the external memory interface in one second. It is worked out by multiplying the card's bus width by its memory clock speed. In the case of DDR RAM, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher 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 applied in one second. This number is worked out by multiplying the total amount of texture units 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 applied in a second.

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