GeForce 9800 GT 1GB vs GeForce GT 640 DDR3

Intro

Compare those specs to the GeForce GT 640 DDR3, which features GPU clock speed of 900 MHz, and 2048 MB of DDR3 RAM running at 1782 MHz through a 128-bit bus. It also is made up of 384 SPUs, 32 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 9800 GT 1GB		105 Watts
	Difference: 40 Watts (62%)

Memory Bandwidth

As far as performance goes, the GeForce 9800 GT 1GB should theoretically be just a bit better than the GeForce GT 640 DDR3 in general. (explain)

GeForce 9800 GT 1GB		57600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 576 (1%)

Texel Rate

The GeForce 9800 GT 1GB should be a little bit (approximately 17%) better at AF than the GeForce GT 640 DDR3. (explain)

GeForce 9800 GT 1GB		33600 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 4800 (17%)

Pixel Rate

If running with a high screen resolution is important to you, then the GeForce GT 640 DDR3 is the winner, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 9800 GT 1GB		9600 Mpixels/sec
	Difference: 4800 (50%)

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 (measured in MB per second) that can be moved over the external memory interface within a second. It is calculated by multiplying the interface width by its memory clock speed. If it uses DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, 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 number of texture map elements (texels) that can be processed per second. This is worked out by multiplying the total texture units by the core clock speed of the chip. The better this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip can possibly write to its local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the number of ROPs by the the core speed of the card. 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 is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.