GeForce GT 640 DDR3 vs GeForce GTX 285 1GB

Intro

Compare all that to the GeForce GTX 285 1GB, which comes with a clock frequency of 648 MHz and a GDDR3 memory speed of 1242 MHz. It also features a 512-bit bus, and uses a 55 nm design. It features 240 SPUs, 80 Texture Address Units, and 32 ROPs.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 285 1GB		204 Watts
	Difference: 139 Watts (214%)

Memory Bandwidth

As far as performance goes, the GeForce GTX 285 1GB should theoretically be quite a bit superior to the GeForce GT 640 DDR3 in general. (explain)

GeForce GTX 285 1GB		158976 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 101952 (179%)

Texel Rate

The GeForce GTX 285 1GB should be quite a bit (more or less 80%) faster with regards to anisotropic filtering than the GeForce GT 640 DDR3. (explain)

GeForce GTX 285 1GB		51840 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 23040 (80%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the GeForce GTX 285 1GB is the winner, and very much so. (explain)

GeForce GTX 285 1GB		20736 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 6336 (44%)

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 (measured in megabytes per second) that can be moved over the external memory interface within a second. It is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, 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 can be processed per second. This figure is calculated by multiplying the total number of texture units by the core speed of the chip. The higher the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.