GeForce GT 640 DDR3 vs GeForce GTX 580 3GB

Intro

Compare those specifications to the GeForce GTX 580 3GB, which has GPU core speed of 772 MHz, and 3072 MB of GDDR5 memory set to run at 1002 MHz through a 384-bit bus. It also features 512 Stream Processors, 64 Texture Address Units, and 48 ROPs.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 580 3GB		244 Watts
	Difference: 179 Watts (275%)

Memory Bandwidth

The GeForce GTX 580 3GB, in theory, should be a lot faster than the GeForce GT 640 DDR3 in general. (explain)

GeForce GTX 580 3GB		192384 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 135360 (237%)

Texel Rate

The GeForce GTX 580 3GB is quite a bit (about 72%) better at AF than the GeForce GT 640 DDR3. (explain)

GeForce GTX 580 3GB		49408 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 20608 (72%)

Pixel Rate

The GeForce GTX 580 3GB will be a lot (about 157%) better at FSAA than the GeForce GT 640 DDR3, and also should be capable of handling higher screen resolutions more effectively. (explain)

GeForce GTX 580 3GB		37056 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 22656 (157%)

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 (counted in megabytes per second) that can be transported past the external memory interface in a second. It is worked out by multiplying the interface width by the speed of its memory. In the case of DDR type RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen 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 of the card by the core clock 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 most pixels that the graphics card can possibly write to the local memory in a 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 - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.