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GeForce GT 640 DDR3 vs GeForce GTX 580 3GB

Intro

The GeForce GT 640 DDR3 comes with 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 Stream Processors, 32 TAUs, and 16 ROPs.

Compare those specifications to the GeForce GTX 580 3GB, which uses a 40 nm design. nVidia has clocked the core frequency at 772 MHz. The GDDR5 RAM works at a speed of 1002 MHz on this specific card. It features 512 SPUs along with 64 Texture Address Units and 48 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 580 3GB 244 Watts
Difference: 179 Watts (275%)

Memory Bandwidth

The GeForce GTX 580 3GB should theoretically perform a lot faster 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 quite a bit (approximately 72%) faster with regards to 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

If using lots of anti-aliasing is important to you, then the GeForce GTX 580 3GB is the winner, by a large margin. (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 (in units of MB per second) that can be moved past the external memory interface within a second. It is worked out by multiplying the interface width by the speed of its memory. In the case of DDR type RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are applied in one second. This figure is worked out by multiplying the total amount of texture units by the core 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 in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill 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 potential to get to the maximum fill rate.

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