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GeForce GT 640 DDR3 vs GeForce GTX 660 Ti

Intro

The GeForce GT 640 DDR3 features a core clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also uses a 128-bit memory bus, and uses a 28 nm design. It is comprised of 384 SPUs, 32 Texture Address Units, and 16 ROPs.

Compare all of that to the GeForce GTX 660 Ti, which features a core clock speed of 915 MHz and a GDDR5 memory frequency of 1500 MHz. It also makes use of a 192-bit memory bus, and uses a 28 nm design. It is made up of 1344 SPUs, 112 Texture Address Units, 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 660 Ti 150 Watts
Difference: 85 Watts (131%)

Memory Bandwidth

Theoretically speaking, the GeForce GTX 660 Ti should perform a lot faster than the GeForce GT 640 DDR3 overall. (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 quite a bit (approximately 256%) more effective at 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

If running with high levels of AA is important to you, then the GeForce GTX 660 Ti is a better choice, by a large margin. (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

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

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: Memory bandwidth is the maximum amount of data (counted in MB per second) that can be moved past the external memory interface in a second. The number is worked out by multiplying the bus width by the speed of its memory. If it uses DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and higher screen 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 texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Render Output Units by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.

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