GeForce GT 640 DDR3 vs Radeon HD 4770

Intro

Compare those specifications to the Radeon HD 4770, which features a GPU core clock speed of 750 MHz, and 512 MB of GDDR5 memory running at 800 MHz through a 128-bit bus. It also is made up of 640(128x5) Stream Processors, 32 TAUs, 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 speaking, the GeForce GT 640 DDR3 should be a small bit faster than the Radeon HD 4770 overall. (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 a bit (about 20%) better at AF 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 bit (more or less 20%) better at AA than the Radeon HD 4770, and also able to handle higher screen resolutions without slowing down too much. (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: Bandwidth is the maximum amount of data (counted in MB per second) that can be transported across the external memory interface in one second. It is worked out by multiplying the card's interface width by its memory speed. If the card has DDR RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied in one second. This number is calculated by multiplying the total amount of texture units by the core speed of the chip. The better this number, the better the video 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 amount of pixels the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the amount of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.