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GeForce GT 640 DDR3 vs GeForce GTX 660 Ti

Intro

The GeForce GT 640 DDR3 has a GPU core speed of 900 MHz, and the 2048 MB of DDR3 RAM runs at 1782 MHz through a 128-bit bus. It also features 384 SPUs, 32 TAUs, and 16 Raster Operation Units.

Compare those specs to the GeForce GTX 660 Ti, which features a clock speed of 915 MHz and a GDDR5 memory frequency of 1500 MHz. It also features a 192-bit bus, and makes use of a 28 nm design. It is comprised of 1344 SPUs, 112 Texture Address Units, and 24 ROPs.

Display Graphs

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(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 better than 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 a lot (approximately 256%) better at AF 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 should be a lot (about 53%) faster with regards to anti-aliasing than the GeForce GT 640 DDR3, and also will be capable of handling higher resolutions without slowing down too much. (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

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GeForce GT 640 DDR3

Amazon.com

GeForce GTX 660 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

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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 11.0 DirectX 11.0
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: Bandwidth is the largest amount of information (measured in MB per second) that can be transported across the external memory interface in a second. It is worked out by multiplying the card's interface width by the speed of its memory. If the card has DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. 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 can be processed per second. This figure is worked out by multiplying the total amount of texture units by the core speed of the chip. The higher this number, the better the video 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 that the graphics chip can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.

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