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GeForce GT 640 DDR3 vs GeForce GTX 650 Ti 2GB

Intro

The GeForce GT 640 DDR3 comes with core speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 RAM. It features 384 SPUs as well as 32 Texture Address Units and 16 Rasterization Operator Units.

Compare that to the GeForce GTX 650 Ti 2GB, which uses a 28 nm design. nVidia has clocked the core frequency at 928 MHz. The GDDR5 RAM is set to run at a speed of 1350 MHz on this specific model. It features 768 SPUs as well as 64 Texture Address Units and 16 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 650 Ti 2GB 110 Watts
Difference: 45 Watts (69%)

Memory Bandwidth

Performance-wise, the GeForce GTX 650 Ti 2GB should theoretically be much better than the GeForce GT 640 DDR3 overall. (explain)

GeForce GTX 650 Ti 2GB 86400 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 29376 (52%)

Texel Rate

The GeForce GTX 650 Ti 2GB will be a lot (more or less 106%) more effective at AF than the GeForce GT 640 DDR3. (explain)

GeForce GTX 650 Ti 2GB 59392 Mtexels/sec
GeForce GT 640 DDR3 28800 Mtexels/sec
Difference: 30592 (106%)

Pixel Rate

If running with high levels of AA is important to you, then the GeForce GTX 650 Ti 2GB is superior to the GeForce GT 640 DDR3, though only just barely. (explain)

GeForce GTX 650 Ti 2GB 14848 Mpixels/sec
GeForce GT 640 DDR3 14400 Mpixels/sec
Difference: 448 (3%)

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 650 Ti 2GB

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 650 Ti 2GB
Manufacturer nVidia nVidia
Year June 2012 October 2012
Code Name GK107 GK106
Fab Process 28 nm 28 nm
Bus PCIe 3.0 x16 PCIe 3.0 x16
Memory 2048 MB 2048 MB
Core Speed 900 MHz 928 MHz
Shader Speed 900 MHz 928 MHz
Memory Speed 1782 MHz (3564 MHz effective) 1350 MHz (5400 MHz effective)
Unified Shaders 384 768
Texture Mapping Units 32 64
Render Output Units 16 16
Bus Type DDR3 GDDR5
Bus Width 128-bit 128-bit
DirectX Version DirectX 11.0 DirectX 11.0
OpenGL Version OpenGL 4.2 OpenGL 4.3
Power (Max TDP) 65 watts 110 watts
Shader Model 5.0 5.0
Bandwidth 57024 MB/sec 86400 MB/sec
Texel Rate 28800 Mtexels/sec 59392 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 14848 Mpixels/sec

Memory Bandwidth: Bandwidth is the max amount of information (counted in megabytes per second) that can be moved across the external memory interface in one second. The number is calculated by multiplying the card's interface width by the speed of its memory. In the case of DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better 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 number of texture map elements (texels) that are applied in one second. This number is calculated 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 card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly write to the local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.

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