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GeForce GT 640 DDR3 vs Radeon HD 4770

Intro

The GeForce GT 640 DDR3 makes use of a 28 nm design. nVidia has set the core speed at 900 MHz. The DDR3 memory runs at a speed of 1782 MHz on this particular model. It features 384 SPUs along with 32 Texture Address Units and 16 Rasterization Operator Units.

Compare all of that to the Radeon HD 4770, which features a core clock frequency of 750 MHz and a GDDR5 memory speed of 800 MHz. It also makes use of a 128-bit bus, and uses a 40 nm design. It is comprised of 640(128x5) SPUs, 32 Texture Address Units, and 16 Raster Operation Units.

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3 65 Watts
Radeon HD 4770 80 Watts
Difference: 15 Watts (23%)

Memory Bandwidth

Theoretically speaking, the GeForce GT 640 DDR3 is 11% faster than the Radeon HD 4770 overall, because of its higher data rate. (explain)

GeForce GT 640 DDR3 57024 MB/sec
Radeon HD 4770 51200 MB/sec
Difference: 5824 (11%)

Texel Rate

The GeForce GT 640 DDR3 will be just a bit (about 20%) faster with regards to anisotropic filtering than the Radeon HD 4770. (explain)

GeForce GT 640 DDR3 28800 Mtexels/sec
Radeon HD 4770 24000 Mtexels/sec
Difference: 4800 (20%)

Pixel Rate

If using a high resolution is important to you, then the GeForce GT 640 DDR3 is a better choice, though only just barely. (explain)

GeForce GT 640 DDR3 14400 Mpixels/sec
Radeon HD 4770 12000 Mpixels/sec
Difference: 2400 (20%)

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 GT 640 DDR3

Amazon.com

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Radeon HD 4770

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 GT 640 DDR3 Radeon HD 4770
Manufacturer nVidia AMD
Year June 2012 Apr 28, 2009
Code Name GK107 RV740
Memory 2048 MB 512 MB
Core Speed 900 MHz 750 MHz
Memory Speed 3564 MHz 3200 MHz
Power (Max TDP) 65 watts 80 watts
Bandwidth 57024 MB/sec 51200 MB/sec
Texel Rate 28800 Mtexels/sec 24000 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 12000 Mpixels/sec
Unified Shaders 384 640(128x5)
Texture Mapping Units 32 32
Render Output Units 16 16
Bus Type DDR3 GDDR5
Bus Width 128-bit 128-bit
Fab Process 28 nm 40 nm
Transistors 1300 million 826 million
Bus PCIe 3.0 x16 PCIe 2.0 x16
DirectX Version DirectX 11.0 DirectX 10.1
OpenGL Version OpenGL 4.2 OpenGL 3.0

Memory Bandwidth: Memory bandwidth is the maximum amount of information (counted in megabytes per second) that can be transported across the external memory interface within a second. It's worked out by multiplying the card's interface width by its memory clock speed. If the card has DDR RAM, it should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly write to its local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Render Output Units 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 also depends on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the max fill rate.

Display Prices

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GeForce GT 640 DDR3

Amazon.com

Check prices at:

Radeon HD 4770

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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