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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 RAM runs at a speed of 1782 MHz on this card. It features 384 SPUs as well as 32 Texture Address Units and 16 ROPs.

Compare all that to the GeForce GTX 260, which comes with GPU clock speed of 576 MHz, and 896 MB of GDDR3 RAM set to run at 999 MHz through a 448-bit bus. It also features 192 SPUs, 64 Texture Address Units, 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 is 96% quicker than the GeForce GT 640 DDR3 in general, because of its higher data rate. (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 (about 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 using high levels of AA is important to you, then the GeForce GTX 260 is a better choice, 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: Memory bandwidth is the largest amount of data (measured in megabytes per second) that can be moved past the external memory interface in a second. It is worked out by multiplying the card's interface width by its memory speed. If the card has DDR RAM, it should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the bandwidth is, 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 processed per second. This figure is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The higher this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the most pixels the video card could possibly write to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. 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 is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.

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