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GeForce 8400 GS 512MB vs GeForce GT 640 DDR3

Intro

The GeForce 8400 GS 512MB features a clock frequency of 650 MHz and a DDR2 memory frequency of 400 MHz. It also features a 64-bit memory bus, and makes use of a 80 nm design. It is comprised of 16 SPUs, 8 TAUs, and 4 Raster Operation Units.

Compare those specifications to the GeForce GT 640 DDR3, which features a clock frequency of 900 MHz and a DDR3 memory speed of 1782 MHz. It also uses a 128-bit bus, and uses a 28 nm design. It features 384 SPUs, 32 TAUs, and 16 ROPs.

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8400 GS 512MB 40 Watts
GeForce GT 640 DDR3 65 Watts
Difference: 25 Watts (63%)

Memory Bandwidth

The GeForce GT 640 DDR3 should in theory be much faster than the GeForce 8400 GS 512MB overall. (explain)

GeForce GT 640 DDR3 57024 MB/sec
GeForce 8400 GS 512MB 6400 MB/sec
Difference: 50624 (791%)

Texel Rate

The GeForce GT 640 DDR3 should be much (more or less 454%) more effective at AF than the GeForce 8400 GS 512MB. (explain)

GeForce GT 640 DDR3 28800 Mtexels/sec
GeForce 8400 GS 512MB 5200 Mtexels/sec
Difference: 23600 (454%)

Pixel Rate

If running with high levels of AA is important to you, then the GeForce GT 640 DDR3 is a better choice, by a large margin. (explain)

GeForce GT 640 DDR3 14400 Mpixels/sec
GeForce 8400 GS 512MB 2600 Mpixels/sec
Difference: 11800 (454%)

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

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GeForce 8400 GS 512MB

Amazon.com

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GeForce GT 640 DDR3

Amazon.com

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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

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Model GeForce 8400 GS 512MB GeForce GT 640 DDR3
Manufacturer nVidia nVidia
Year June 2007 June 2012
Code Name G86 GK107
Memory 512 MB 2048 MB
Core Speed 650 MHz 900 MHz
Memory Speed 800 MHz 3564 MHz
Power (Max TDP) 40 watts 65 watts
Bandwidth 6400 MB/sec 57024 MB/sec
Texel Rate 5200 Mtexels/sec 28800 Mtexels/sec
Pixel Rate 2600 Mpixels/sec 14400 Mpixels/sec
Unified Shaders 16 384
Texture Mapping Units 8 32
Render Output Units 4 16
Bus Type DDR2 DDR3
Bus Width 64-bit 128-bit
Fab Process 80 nm 28 nm
Transistors 210 million 1300 million
Bus PCIe x16, PCI PCIe 3.0 x16
DirectX Version DirectX 10 DirectX 11.0
OpenGL Version OpenGL 3.0 OpenGL 4.2

Memory Bandwidth: Memory bandwidth is the max amount of data (counted in megabytes per second) that can be moved across the external memory interface in a second. It is calculated by multiplying the interface width by the speed of its memory. If the card has DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the faster 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 number of texture map elements (texels) that are processed per second. This 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 graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also 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 of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.

Display Prices

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GeForce 8400 GS 512MB

Amazon.com

Check prices at:

GeForce GT 640 DDR3

Amazon.com

Check prices at:

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.

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