GeForce 8800 GTX vs GeForce GT 640 DDR3

Intro

Compare all that to the GeForce GT 640 DDR3, which uses a 28 nm design. nVidia has set the core speed at 900 MHz. The DDR3 memory runs at a frequency of 1782 MHz on this specific card. It features 384 SPUs along with 32 Texture Address Units and 16 ROPs.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 GTX		155 Watts
	Difference: 90 Watts (138%)

Memory Bandwidth

As far as performance goes, the GeForce 8800 GTX should theoretically be a lot better than the GeForce GT 640 DDR3 overall. (explain)

GeForce 8800 GTX		86400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 29376 (52%)

Texel Rate

The GeForce 8800 GTX will be quite a bit (more or less 28%) faster with regards to AF than the GeForce GT 640 DDR3. (explain)

GeForce 8800 GTX		36800 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 8000 (28%)

Pixel Rate

The GeForce GT 640 DDR3 will be a small bit (about 4%) more effective at AA than the GeForce 8800 GTX, and should be capable of handling higher resolutions without slowing down too much. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 GTX		13800 Mpixels/sec
	Difference: 600 (4%)

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 data (in units of MB per second) that can be transported past the external memory interface within a second. The number is worked out by multiplying the card's bus width by its memory clock speed. If the card has DDR memory, it should be multiplied by 2 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 AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.