GeForce 8800 Ultra vs GeForce GT 640 DDR3

Intro

Compare those specs to the GeForce GT 640 DDR3, which has GPU core speed of 900 MHz, and 2048 MB of DDR3 RAM set to run at 1782 MHz through a 128-bit bus. It also features 384 SPUs, 32 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 Ultra		171 Watts
	Difference: 106 Watts (163%)

Memory Bandwidth

The GeForce 8800 Ultra should in theory be quite a bit faster than the GeForce GT 640 DDR3 overall. (explain)

GeForce 8800 Ultra		103680 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 46656 (82%)

Texel Rate

The GeForce 8800 Ultra will be quite a bit (about 36%) better at texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce 8800 Ultra		39168 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 10368 (36%)

Pixel Rate

If using a high screen resolution is important to you, then the GeForce 8800 Ultra is superior to the GeForce GT 640 DDR3, though only just barely. (explain)

GeForce 8800 Ultra		14688 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 288 (2%)

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 maximum amount of data (counted in megabytes per second) that can be transferred past the external memory interface in a second. It's worked out by multiplying the card's bus width by the speed of its memory. If the card has DDR RAM, it should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are processed in one second. This number is calculated by multiplying the total number of texture units by the core speed of the chip. The better 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 in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip could possibly record to its 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 core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.