GeForce 8800 GTS (G80) 320MB vs GeForce GT 640 DDR3

Intro

Compare all of that to the GeForce GT 640 DDR3, which features a clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also features a 128-bit memory bus, and uses a 28 nm design. It is made up of 384 SPUs, 32 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 GTS (G80) 320MB		143 Watts
	Difference: 78 Watts (120%)

Memory Bandwidth

The GeForce 8800 GTS (G80) 320MB, in theory, should perform a small bit faster than the GeForce GT 640 DDR3 overall. (explain)

GeForce 8800 GTS (G80) 320MB		63360 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 6336 (11%)

Texel Rate

The GeForce GT 640 DDR3 will be a little bit (approximately 17%) better at anisotropic filtering than the GeForce 8800 GTS (G80) 320MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8800 GTS (G80) 320MB		24624 Mtexels/sec
	Difference: 4176 (17%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is a better choice, and very much so. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 GTS (G80) 320MB		10260 Mpixels/sec
	Difference: 4140 (40%)

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 largest amount of data (counted in megabytes per second) that can be transported across the external memory interface in one second. It's calculated by multiplying the card's interface width by its memory speed. In the case of DDR RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This figure is calculated by multiplying the total number of texture units by the core speed of the chip. The higher this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card can possibly record to its local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.