GeForce GT 640 DDR3 vs GeForce GTX 260

Intro

Compare those specifications to the GeForce GTX 260, which uses a 65 nm design. nVidia has set the core frequency at 576 MHz. The GDDR3 RAM is set to run at a frequency of 999 MHz on this particular model. It features 192 SPUs along with 64 Texture Address Units and 28 ROPs.

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, in theory, should perform 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 will be much (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 will be a small bit (more or less 12%) faster with regards to 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: Bandwidth is the maximum amount of data (in units of MB per second) that can be moved past the external memory interface in one second. The number is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's 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 texture map elements (texels) that can be applied in one second. This number is worked out by multiplying the total texture units of the card by the core clock speed of the chip. The better this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the most pixels that the graphics card can possibly write to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.