GeForce 8800 GT 256MB vs GeForce GT 640 DDR3

Intro

Compare that to the GeForce GT 640 DDR3, which has a core clock speed of 900 MHz and a DDR3 memory speed of 1782 MHz. It also features a 128-bit memory bus, and makes use of a 28 nm design. It features 384 SPUs, 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 GT 256MB		105 Watts
	Difference: 40 Watts (62%)

Memory Bandwidth

Theoretically speaking, the GeForce GT 640 DDR3 should be 27% faster than the GeForce 8800 GT 256MB in general, because of its higher data rate. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8800 GT 256MB		44800 MB/sec
	Difference: 12224 (27%)

Texel Rate

The GeForce 8800 GT 256MB should be a small bit (about 17%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce 8800 GT 256MB		33600 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 4800 (17%)

Pixel Rate

If using a high screen resolution is important to you, then the GeForce GT 640 DDR3 is superior to the GeForce 8800 GT 256MB, by far. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 GT 256MB		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: Memory bandwidth is the max amount of information (counted in MB per second) that can be moved across the external memory interface within a second. It is calculated by multiplying the card's interface width by its memory clock speed. In the case of DDR memory, the result should be multiplied by 2 once again. If 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 processed per second. This number is calculated by multiplying the total number of texture units by the core clock speed of the chip. The better this number, the better the video 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 most pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out 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 fill rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.