GeForce GT 640 DDR3 vs Radeon HD 4770

Intro

Compare those specifications to the Radeon HD 4770, which features a core clock speed 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 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, the GeForce GT 640 DDR3 should perform 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 should be a small bit (approximately 20%) more effective at texture 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 should be just a bit (approximately 20%) more effective at full screen anti-aliasing than the Radeon HD 4770, and also will be able to handle higher screen resolutions without losing too much performance. (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 (in units of MB per second) that can be transported over the external memory interface in one second. It's calculated by multiplying the card's interface width by its memory clock speed. If it uses DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better 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 number of texture map elements (texels) that are processed in one second. This figure is worked out by multiplying the total texture units of the card by the core speed of the chip. The higher this number, the better the video 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 amount of pixels that the graphics chip could possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.