GeForce GT 640 DDR3 vs Radeon HD 5870

Intro

Compare those specifications to the Radeon HD 5870, which uses a 40 nm design. AMD has clocked the core frequency at 850 MHz. The GDDR5 RAM works at a frequency of 1200 MHz on this specific card. It features 1600(320x5) SPUs as well as 80 Texture Address Units and 32 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 5870		188 Watts
	Difference: 123 Watts (189%)

Memory Bandwidth

As far as performance goes, the Radeon HD 5870 should in theory be a lot better than the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 5870		153600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 96576 (169%)

Texel Rate

The Radeon HD 5870 should be quite a bit (approximately 136%) more effective at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 5870		68000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 39200 (136%)

Pixel Rate

If running with high levels of AA is important to you, then the Radeon HD 5870 is the winner, by a large margin. (explain)

Radeon HD 5870		27200 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 12800 (89%)

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 maximum amount of data (counted in megabytes per second) that can be transferred over the external memory interface in a second. It's calculated by multiplying the bus width by its memory speed. If the card has DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high 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 amount of texture units by the core clock speed of the chip. The better this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number 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 drawing the pixels (image) on the screen. The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.