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GeForce GT 640 DDR3 vs GeForce GTX 660 Ti

Intro

The GeForce GT 640 DDR3 uses a 28 nm design. nVidia has set the core speed at 900 MHz. The DDR3 RAM is set to run at a speed of 1782 MHz on this specific model. It features 384 SPUs along with 32 TAUs and 16 ROPs.

Compare all that to the GeForce GTX 660 Ti, which uses a 28 nm design. nVidia has set the core frequency at 915 MHz. The GDDR5 memory runs at a frequency of 1500 MHz on this model. It features 1344 SPUs as well as 112 Texture Address Units and 24 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 660 Ti 150 Watts
Difference: 85 Watts (131%)

Memory Bandwidth

As far as performance goes, the GeForce GTX 660 Ti should theoretically be much superior to the GeForce GT 640 DDR3 in general. (explain)

GeForce GTX 660 Ti 144000 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 86976 (153%)

Texel Rate

The GeForce GTX 660 Ti should be much (more or less 256%) faster with regards to texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce GTX 660 Ti 102480 Mtexels/sec
GeForce GT 640 DDR3 28800 Mtexels/sec
Difference: 73680 (256%)

Pixel Rate

The GeForce GTX 660 Ti will be quite a bit (approximately 53%) more effective at full screen anti-aliasing than the GeForce GT 640 DDR3, and also will be able to handle higher screen resolutions more effectively. (explain)

GeForce GTX 660 Ti 21960 Mpixels/sec
GeForce GT 640 DDR3 14400 Mpixels/sec
Difference: 7560 (53%)

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

Please note that the price comparisons are based on search keywords, and might not be the exact same card listed on this page. We have no control over the accuracy of their search results.

GeForce GT 640 DDR3

Amazon.com

Other US-based stores

GeForce GTX 660 Ti

Amazon.com

Other US-based stores

Specifications

Model GeForce GT 640 DDR3 GeForce GTX 660 Ti
Manufacturer nVidia nVidia
Year June 2012 August 2012
Code Name GK107 GK104
Fab Process 28 nm 28 nm
Bus PCIe 3.0 x16 PCIe 3.0 x16
Memory 2048 MB 2048 MB
Core Speed 900 MHz 915 MHz
Shader Speed 900 MHz 915 MHz
Memory Speed 1782 MHz (3564 MHz effective) 1500 MHz (6000 MHz effective)
Unified Shaders 384 1344
Texture Mapping Units 32 112
Render Output Units 16 24
Bus Type DDR3 GDDR5
Bus Width 128-bit 192-bit
DirectX Version DirectX 11.1 DirectX 11.1
OpenGL Version OpenGL 4.2 OpenGL 4.3
Power (Max TDP) 65 watts 150 watts
Shader Model 5.0 5.0
Bandwidth 57024 MB/sec 144000 MB/sec
Texel Rate 28800 Mtexels/sec 102480 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 21960 Mpixels/sec

Memory Bandwidth: Memory bandwidth is the max amount of information (counted in MB per second) that can be transported over the external memory interface in one second. The number is calculated by multiplying the card's bus width by its memory clock speed. If the card has DDR type memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better 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 amount of texture map elements (texels) that can be processed per second. This number is calculated by multiplying the total texture units of the card by the core speed of the chip. The higher this number, 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 number of pixels the graphics card could possibly record to its local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the number 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 lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.

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