GeForce 9800 GTX vs GeForce GT 640 DDR3

Intro

Compare those specs to the GeForce GT 640 DDR3, which makes use of a 28 nm design. nVidia has clocked the core speed at 900 MHz. The DDR3 RAM works at a speed of 1782 MHz on this particular model. It features 384 SPUs along with 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

As far as performance goes, the GeForce 9800 GTX should in theory be much better than the GeForce GT 640 DDR3 overall. (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 (more or less 50%) faster with regards to anisotropic filtering 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 running with high levels of AA is important to you, then the GeForce GT 640 DDR3 is superior to the GeForce 9800 GTX, and very much so. (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 (measured in megabytes per second) that can be transferred over the external memory interface within a second. It's calculated by multiplying the card's interface width by its memory clock speed. If it uses DDR memory, it should be multiplied by 2 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 anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied per second. This number is calculated by multiplying the total texture units by the core speed of the chip. The higher 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 video card could possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.