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GeForce GT 640 DDR3 vs GeForce GTX 550 Ti

Intro

The GeForce GT 640 DDR3 features a GPU clock speed of 900 MHz, and the 2048 MB of DDR3 RAM is set to run at 1782 MHz through a 128-bit bus. It also is comprised of 384 Stream Processors, 32 Texture Address Units, and 16 ROPs.

Compare all that to the GeForce GTX 550 Ti, which features GPU clock speed of 900 MHz, and 1024 MB of GDDR5 RAM running at 1026 MHz through a 192-bit bus. It also is comprised of 192 SPUs, 32 Texture Address Units, and 24 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 550 Ti 116 Watts
Difference: 51 Watts (78%)

Memory Bandwidth

Theoretically speaking, the GeForce GTX 550 Ti is 73% faster than the GeForce GT 640 DDR3 in general, because of its higher data rate. (explain)

GeForce GTX 550 Ti 98496 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 41472 (73%)

Texel Rate

Both cards have exactly the same texel fill rate, so theoretically they should perform equally good at at anisotropic filtering. (explain)

Pixel Rate

The GeForce GTX 550 Ti is much (about 50%) better at full screen anti-aliasing than the GeForce GT 640 DDR3, and will be able to handle higher resolutions without slowing down too much. (explain)

GeForce GTX 550 Ti 21600 Mpixels/sec
GeForce GT 640 DDR3 14400 Mpixels/sec
Difference: 7200 (50%)

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 550 Ti

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 550 Ti
Manufacturer nVidia nVidia
Year June 2012 March 2011
Code Name GK107 GF116
Fab Process 28 nm 40 nm
Bus PCIe 3.0 x16 PCIe 2.1 x16
Memory 2048 MB 1024 MB
Core Speed 900 MHz 900 MHz
Shader Speed 900 MHz 1800 MHz
Memory Speed 1782 MHz (3564 MHz effective) 1026 MHz (4104 MHz effective)
Unified Shaders 384 192
Texture Mapping Units 32 32
Render Output Units 16 24
Bus Type DDR3 GDDR5
Bus Width 128-bit 192-bit
DirectX Version DirectX 11.0 DirectX 11
OpenGL Version OpenGL 4.2 OpenGL 4.1
Power (Max TDP) 65 watts 116 watts
Shader Model 5.0 5.0
Bandwidth 57024 MB/sec 98496 MB/sec
Texel Rate 28800 Mtexels/sec 28800 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 21600 Mpixels/sec

Memory Bandwidth: Bandwidth is the largest amount of data (measured in MB per second) that can be transported across the external memory interface within a second. It's calculated by multiplying the interface width by its memory clock speed. If the card has DDR memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied in one second. This figure 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 texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.

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