GeForce GT 640 DDR3 vs Radeon HD 4770

Intro

Compare those specs to the Radeon HD 4770, which comes with GPU clock speed of 750 MHz, and 512 MB of GDDR5 RAM set to run at 800 MHz through a 128-bit bus. It also is comprised of 640(128x5) SPUs, 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 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 bit (about 20%) more effective 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 will be a small bit (more or less 20%) more effective at FSAA than the Radeon HD 4770, and also will be able to handle higher resolutions while still performing well. (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 information (in units of MB per second) that can be transferred over the external memory interface in a second. It is worked out by multiplying the interface width by its memory clock speed. If the card has DDR type RAM, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, 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 number of texture map elements (texels) that can be applied per second. This number is calculated by multiplying the total number of texture units of the card by the core speed of the chip. The higher this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly record to its local memory in one second - measured in millions of pixels per second. The figure is calculated 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 is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.