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GeForce GT 640 DDR3 vs Radeon HD 4850 2GB

Intro

The GeForce GT 640 DDR3 has a clock frequency of 900 MHz and a DDR3 memory speed of 1782 MHz. It also makes use of a 128-bit bus, and uses a 28 nm design. It features 384 SPUs, 32 TAUs, and 16 Raster Operation Units.

Compare all of that to the Radeon HD 4850 2GB, which comes with GPU clock speed of 625 MHz, and 2048 MB of GDDR4 memory running at 993 MHz through a 256-bit bus. It also is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 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
Radeon HD 4850 2GB 110 Watts
Difference: 45 Watts (69%)

Memory Bandwidth

The Radeon HD 4850 2GB should theoretically perform a small bit faster than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4850 2GB 63552 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 6528 (11%)

Texel Rate

The GeForce GT 640 DDR3 will be a small bit (more or less 15%) faster with regards to texture filtering than the Radeon HD 4850 2GB. (explain)

GeForce GT 640 DDR3 28800 Mtexels/sec
Radeon HD 4850 2GB 25000 Mtexels/sec
Difference: 3800 (15%)

Pixel Rate

The GeForce GT 640 DDR3 is much (approximately 44%) more effective at full screen anti-aliasing than the Radeon HD 4850 2GB, and also should be capable of handling higher resolutions more effectively. (explain)

GeForce GT 640 DDR3 14400 Mpixels/sec
Radeon HD 4850 2GB 10000 Mpixels/sec
Difference: 4400 (44%)

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

Radeon HD 4850 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 Radeon HD 4850 2GB
Manufacturer nVidia AMD
Year June 2012 Jun 25, 2008
Code Name GK107 RV770 PRO
Fab Process 28 nm 55 nm
Bus PCIe 3.0 x16 PCIe 2.0 x16
Memory 2048 MB 2048 MB
Core Speed 900 MHz 625 MHz
Shader Speed 900 MHz (N/A) MHz
Memory Speed 1782 MHz (3564 MHz effective) 993 MHz (1986 MHz effective)
Unified Shaders 384 800(160x5)
Texture Mapping Units 32 40
Render Output Units 16 16
Bus Type DDR3 GDDR4
Bus Width 128-bit 256-bit
DirectX Version DirectX 11.0 DirectX 10.1
OpenGL Version OpenGL 4.2 OpenGL 3.0
Power (Max TDP) 65 watts 110 watts
Shader Model 5.0 4.1
Bandwidth 57024 MB/sec 63552 MB/sec
Texel Rate 28800 Mtexels/sec 25000 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 10000 Mpixels/sec

Memory Bandwidth: Bandwidth is the maximum amount of information (in units of MB per second) that can be transferred across the external memory interface in a second. It is calculated by multiplying the card's interface width by its memory speed. If the card has DDR type memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied in one second. This is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly record to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.

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