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GeForce GT 640 DDR3 vs Radeon HD 4850 2GB

Intro

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

Compare those specs to the Radeon HD 4850 2GB, which features core clock speeds of 625 MHz on the GPU, and 993 MHz on the 2048 MB of GDDR4 memory. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 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
Radeon HD 4850 2GB 110 Watts
Difference: 45 Watts (69%)

Memory Bandwidth

The Radeon HD 4850 2GB should theoretically be a small bit faster than the GeForce GT 640 DDR3 overall. (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 bit (more or less 15%) faster with regards to anisotropic 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

If using a high screen resolution is important to you, then the GeForce GT 640 DDR3 is a better choice, and very much so. (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 max amount of data (measured in MB per second) that can be moved over the external memory interface within a second. It's calculated by multiplying the card's interface width by its memory speed. If the card has DDR type RAM, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount 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 clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.

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