GeForce GT 640 DDR3 vs Radeon HD 3870 1GB

Intro

Compare those specs to the Radeon HD 3870 1GB, which features a GPU core clock speed of 775 MHz, and 1024 MB of GDDR4 RAM running at 1125 MHz through a 256-bit bus. It also is made up of 320(64x5) Stream Processors, 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 3870 1GB		106 Watts
	Difference: 41 Watts (63%)

Memory Bandwidth

Theoretically, the Radeon HD 3870 1GB should perform much faster than the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 3870 1GB		72000 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 14976 (26%)

Texel Rate

The GeForce GT 640 DDR3 should be quite a bit (about 132%) more effective at AF than the Radeon HD 3870 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3870 1GB		12400 Mtexels/sec
	Difference: 16400 (132%)

Pixel Rate

The GeForce GT 640 DDR3 is just a bit (about 16%) faster with regards to anti-aliasing than the Radeon HD 3870 1GB, and also will be capable of handling higher screen resolutions while still performing well. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 3870 1GB		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: Bandwidth is the max amount of information (measured in MB per second) that can be transported over the external memory interface in a second. The number is worked out by multiplying the card's bus width by its memory speed. In the case of DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. 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 texture map elements (texels) that can be applied in one second. This is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly write to the local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.