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GeForce GT 640 DDR3 vs GeForce GTX 260

Intro

The GeForce GT 640 DDR3 makes use of a 28 nm design. nVidia has set the core frequency at 900 MHz. The DDR3 memory runs at a speed of 1782 MHz on this specific model. It features 384 SPUs as well as 32 Texture Address Units and 16 Rasterization Operator Units.

Compare all that to the GeForce GTX 260, which makes use of a 65 nm design. nVidia has clocked the core speed at 576 MHz. The GDDR3 RAM runs at a frequency of 999 MHz on this particular card. It features 192 SPUs as well as 64 TAUs and 28 ROPs.

(No game benchmarks for this combination yet.)

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

Theoretically speaking, the GeForce GTX 260 should be a lot faster than the GeForce GT 640 DDR3 in general. (explain)

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

Texel Rate

The GeForce GTX 260 is quite a bit (about 28%) faster with regards to texture filtering 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

If using lots of anti-aliasing is important to you, then the GeForce GTX 260 is superior to the GeForce GT 640 DDR3, not by a very large margin though. (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

GeForce GT 640 DDR3

Amazon.com

GeForce GTX 260

Amazon.com

Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

Specifications

Model GeForce GT 640 DDR3 GeForce GTX 260
Manufacturer nVidia nVidia
Year June 2012 June 16, 2008
Code Name GK107 G200
Fab Process 28 nm 65 nm
Bus PCIe 3.0 x16 PCIe x16 2.0
Memory 2048 MB 896 MB
Core Speed 900 MHz 576 MHz
Shader Speed 900 MHz 1242 MHz
Memory Speed 1782 MHz (3564 MHz effective) 999 MHz (1998 MHz effective)
Unified Shaders 384 192
Texture Mapping Units 32 64
Render Output Units 16 28
Bus Type DDR3 GDDR3
Bus Width 128-bit 448-bit
DirectX Version DirectX 11.0 DirectX 10
OpenGL Version OpenGL 4.2 OpenGL 3.1
Power (Max TDP) 65 watts 182 watts
Shader Model 5.0 4.0
Bandwidth 57024 MB/sec 111888 MB/sec
Texel Rate 28800 Mtexels/sec 36864 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 16128 Mpixels/sec

Memory Bandwidth: Memory bandwidth is the largest amount of data (in units of MB per second) that can be moved over the external memory interface in one second. It is worked out by multiplying the card's interface width by the speed of its memory. If the card has DDR RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be processed in one second. This is worked out by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the 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 maximum number of pixels that the graphics chip could possibly record to the local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the number of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the max fill rate.

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