GeForce GT 640 DDR3 vs Radeon HD 4770

Intro

Compare those specs to the Radeon HD 4770, which comes with a core clock frequency of 750 MHz and a GDDR5 memory speed of 800 MHz. It also features a 128-bit memory bus, and uses a 40 nm design. It features 640(128x5) SPUs, 32 Texture Address Units, and 16 ROPs.

Display Graphs

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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, the GeForce GT 640 DDR3 should be a small bit faster than the Radeon HD 4770 in general. (explain)

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

Texel Rate

The GeForce GT 640 DDR3 is a small bit (approximately 20%) more effective at 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

The GeForce GT 640 DDR3 is a little bit (about 20%) more effective at full screen anti-aliasing than the Radeon HD 4770, and also should be able to handle higher screen resolutions better. (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

Specifications

Memory Bandwidth: Memory bandwidth is the maximum amount of information (counted in MB per second) that can be transported past the external memory interface in one second. It is calculated by multiplying the interface width by the speed of its memory. In the case of DDR type RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This figure is worked out by multiplying the total number of texture units by the core speed of the chip. The higher this number, the better the graphics card will be at 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 the video card could possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.