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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 clocked the core frequency at 900 MHz. The DDR3 memory is set to run at a speed of 1782 MHz on this particular card. It features 384 SPUs along with 32 TAUs and 16 Rasterization Operator Units.

Compare all of that to the GeForce GTX 260, which features GPU core speed of 576 MHz, and 896 MB of GDDR3 memory set to run at 999 MHz through a 448-bit bus. It also is made up of 192 Stream Processors, 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

In theory, the GeForce GTX 260 will be 96% faster than the GeForce GT 640 DDR3 overall, because of its higher bandwidth. (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 quite a bit (more or less 28%) faster with regards to anisotropic 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 running with a high screen resolution is important to you, then the GeForce GTX 260 is the winner, but it probably won't make a huge difference. (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: Bandwidth is the max amount of data (counted in megabytes per second) that can be transported over the external memory interface in one second. The number is worked out by multiplying the card's bus width by its memory speed. In the case of DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This is worked out by multiplying the total amount of texture units by the core speed of the chip. The better this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly record to the local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the amount of Render Output Units by the the card's 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 reach the maximum fill rate.

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