GeForce 9800 GTX vs GeForce GT 640 DDR3

Intro

Compare those specifications to the GeForce GT 640 DDR3, which uses a 28 nm design. nVidia has clocked the core speed at 900 MHz. The DDR3 memory runs at a frequency of 1782 MHz on this particular card. It features 384 SPUs as well as 32 TAUs and 16 Rasterization Operator Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 9800 GTX		140 Watts
	Difference: 75 Watts (115%)

Memory Bandwidth

In theory, the GeForce 9800 GTX should be 23% faster than the GeForce GT 640 DDR3 in general, due to its higher data rate. (explain)

GeForce 9800 GTX		70400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 13376 (23%)

Texel Rate

The GeForce 9800 GTX is much (about 50%) better at AF than the GeForce GT 640 DDR3. (explain)

GeForce 9800 GTX		43200 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 14400 (50%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is a better choice, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 9800 GTX		10800 Mpixels/sec
	Difference: 3600 (33%)

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 (counted in MB per second) that can be transferred over the external memory interface within a second. It's worked out by multiplying the bus width by the speed of its memory. If it uses DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. 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 processed per second. This number is calculated by multiplying the total number of texture units of the card by the core speed of the chip. The better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate 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 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 memory bandwidth is, the lower the ability to get to the maximum fill rate.