GeForce GT 640 DDR3 vs GeForce GTX 260

Intro

Compare those specs to the GeForce GTX 260, which uses a 65 nm design. nVidia has set the core frequency at 576 MHz. The GDDR3 memory works at a speed of 999 MHz on this model. It features 192 SPUs as well as 64 Texture Address Units and 28 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 260		182 Watts
	Difference: 117 Watts (180%)

Memory Bandwidth

The GeForce GTX 260 should in theory be a lot faster than the GeForce GT 640 DDR3 overall. (explain)

GeForce GTX 260		111888 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 54864 (96%)

Texel Rate

The GeForce GTX 260 should be a lot (more or less 28%) faster with regards to AF than the GeForce GT 640 DDR3. (explain)

GeForce GTX 260		36864 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 8064 (28%)

Pixel Rate

The GeForce GTX 260 should be just a bit (more or less 12%) better at FSAA than the GeForce GT 640 DDR3, and also will be able to handle higher screen resolutions while still performing well. (explain)

GeForce GTX 260		16128 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 1728 (12%)

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 (in units of MB per second) that can be transferred over 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 memory, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This is calculated by multiplying the total amount of texture units by the core speed of the chip. The higher this number, the better the video 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 write to its local memory in one second - measured in millions of pixels per second. Pixel rate 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 drawing the pixels (image) on the screen. The actual pixel fill rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.