GeForce GT 640 DDR3 vs Radeon HD 3870 512MB

Intro

Compare those specs to the Radeon HD 3870 512MB, which uses a 55 nm design. AMD has clocked the core speed at 775 MHz. The GDDR3 RAM runs at a speed of 900 MHz on this specific model. It features 320(64x5) SPUs along with 16 TAUs 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 512MB		106 Watts
	Difference: 41 Watts (63%)

Memory Bandwidth

Performance-wise, the Radeon HD 3870 512MB should theoretically be a small 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 should be a lot (approximately 132%) faster with regards to 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 is a little bit (more or less 16%) better at full screen anti-aliasing than the Radeon HD 3870 512MB, and will be capable of handling higher screen resolutions while still performing well. (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 (measured in megabytes per second) that can be moved across the external memory interface in one second. The number is calculated by multiplying the card's bus width by its memory speed. If the card has DDR memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better the card's 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 amount of texture map elements (texels) that are processed in one second. This is worked out by multiplying the total texture units of the card by the core clock speed of the chip. The better this number, 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 maximum amount of pixels that the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.