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GeForce GT 640 DDR3 vs GeForce GTX 550 Ti

Intro

The GeForce GT 640 DDR3 features a GPU core clock speed of 900 MHz, and the 2048 MB of DDR3 memory runs at 1782 MHz through a 128-bit bus. It also is made up of 384 SPUs, 32 Texture Address Units, and 16 ROPs.

Compare all that to the GeForce GTX 550 Ti, which has a clock speed of 900 MHz and a GDDR5 memory frequency of 1026 MHz. It also uses a 192-bit bus, and uses a 40 nm design. It features 192 SPUs, 32 TAUs, 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

The GeForce GTX 550 Ti should in theory perform much faster than the GeForce GT 640 DDR3 overall. (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 be equally good at at AF. (explain)

Pixel Rate

If using a high resolution is important to you, then the GeForce GTX 550 Ti is a better choice, and very much so. (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: Memory bandwidth is the maximum amount of data (in units of megabytes per second) that can be transported across the external memory interface in a second. The number is calculated by multiplying the bus width by its memory clock speed. In the case of DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

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