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GeForce GT 640 DDR3 vs GeForce GTX 660 Ti

Intro

The GeForce GT 640 DDR3 makes use of a 28 nm design. nVidia has set the core speed at 900 MHz. The DDR3 RAM works at a frequency of 1782 MHz on this specific model. It features 384 SPUs along with 32 TAUs and 16 Rasterization Operator Units.

Compare all that to the GeForce GTX 660 Ti, which has a core clock speed of 915 MHz and a GDDR5 memory speed of 1500 MHz. It also features a 192-bit memory bus, and makes use of a 28 nm design. It is made up of 1344 SPUs, 112 Texture Address Units, and 24 Raster Operation 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

The GeForce GTX 660 Ti should in theory be quite a bit faster 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 will be a lot (approximately 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 is quite a bit (approximately 53%) better at FSAA than the GeForce GT 640 DDR3, and also should 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

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: Bandwidth is the maximum amount of information (counted in MB per second) that can be transported over the external memory interface in a second. It's worked out by multiplying the bus width by its memory clock speed. In the case of DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one 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 the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the most pixels the video card could possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of colour ROPs by the the core 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 also depends on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.

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