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GeForce GT 640 DDR3 vs GeForce GTX 580 3GB

Intro

The GeForce GT 640 DDR3 features a GPU core clock speed of 900 MHz, and the 2048 MB of DDR3 RAM is set to run at 1782 MHz through a 128-bit bus. It also features 384 Stream Processors, 32 Texture Address Units, and 16 ROPs.

Compare those specs to the GeForce GTX 580 3GB, which comes with GPU clock speed of 772 MHz, and 3072 MB of GDDR5 RAM running at 1002 MHz through a 384-bit bus. It also is comprised of 512 Stream Processors, 64 TAUs, and 48 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 580 3GB 244 Watts
Difference: 179 Watts (275%)

Memory Bandwidth

Performance-wise, the GeForce GTX 580 3GB should theoretically be much better than the GeForce GT 640 DDR3 overall. (explain)

GeForce GTX 580 3GB 192384 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 135360 (237%)

Texel Rate

The GeForce GTX 580 3GB is much (approximately 72%) better at AF than the GeForce GT 640 DDR3. (explain)

GeForce GTX 580 3GB 49408 Mtexels/sec
GeForce GT 640 DDR3 28800 Mtexels/sec
Difference: 20608 (72%)

Pixel Rate

The GeForce GTX 580 3GB is much (approximately 157%) more effective at full screen anti-aliasing than the GeForce GT 640 DDR3, and capable of handling higher resolutions without losing too much performance. (explain)

GeForce GTX 580 3GB 37056 Mpixels/sec
GeForce GT 640 DDR3 14400 Mpixels/sec
Difference: 22656 (157%)

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 580 3GB

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 580 3GB
Manufacturer nVidia nVidia
Year June 2012 November 2010
Code Name GK107 GF110
Fab Process 28 nm 40 nm
Bus PCIe 3.0 x16 PCIe x16
Memory 2048 MB 3072 MB
Core Speed 900 MHz 772 MHz
Shader Speed 900 MHz 1544 MHz
Memory Speed 1782 MHz (3564 MHz effective) 1002 MHz (4008 MHz effective)
Unified Shaders 384 512
Texture Mapping Units 32 64
Render Output Units 16 48
Bus Type DDR3 GDDR5
Bus Width 128-bit 384-bit
DirectX Version DirectX 11.0 DirectX 11
OpenGL Version OpenGL 4.2 OpenGL 4.1
Power (Max TDP) 65 watts 244 watts
Shader Model 5.0 5.0
Bandwidth 57024 MB/sec 192384 MB/sec
Texel Rate 28800 Mtexels/sec 49408 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 37056 Mpixels/sec

Memory Bandwidth: Bandwidth is the max amount of data (counted in megabytes per second) that can be transported over the external memory interface in a second. The number is worked out by multiplying the card's bus width by its memory clock speed. In the case of DDR memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This number is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better this number, 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 maximum number of pixels the video card can possibly record to its local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.

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