GeForce 8800 GT 1GB vs GeForce GT 640 DDR3

Intro

Compare those specifications to the GeForce GT 640 DDR3, which has a GPU core 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 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 GT 1GB		105 Watts
	Difference: 40 Watts (62%)

Memory Bandwidth

As far as performance goes, the GeForce 8800 GT 1GB should theoretically be just a bit superior to the GeForce GT 640 DDR3 in general. (explain)

GeForce 8800 GT 1GB		57600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 576 (1%)

Texel Rate

The GeForce 8800 GT 1GB is a small bit (more or less 17%) better at texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce 8800 GT 1GB		33600 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 4800 (17%)

Pixel Rate

The GeForce GT 640 DDR3 is quite a bit (about 50%) more effective at anti-aliasing than the GeForce 8800 GT 1GB, and will be capable of handling higher resolutions better. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 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 max amount of data (in units of megabytes per second) that can be moved past the external memory interface in a second. It is calculated by multiplying the bus width by the speed of its memory. If it uses DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed in one second. This is worked out by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.