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GeForce GT 640 DDR3 vs GeForce GTX 260

Intro

The GeForce GT 640 DDR3 comes with core clock speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 memory. It features 384 SPUs along with 32 TAUs and 16 Rasterization Operator Units.

Compare all of 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 model. It features 192 SPUs along with 64 Texture Address Units and 28 Rasterization Operator Units.

(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 in general, due to 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 a lot (more or less 28%) better at 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

If running with lots of anti-aliasing is important to you, then the GeForce GTX 260 is a better choice, though only just barely. (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 max amount of information (counted in megabytes per second) that can be moved past the external memory interface in a second. It's calculated by multiplying the interface width by its memory clock speed. If the card has DDR type memory, it should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the 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 number of texture map elements (texels) that are processed per second. This figure is calculated by multiplying the total amount of texture units by the core speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip could possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Render Output Units by the clock 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 rate also depends on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.

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