GeForce GT 640 DDR3 vs Radeon HD 5770

Intro

Compare all of that to the Radeon HD 5770, which has core clock speeds of 850 MHz on the GPU, and 1200 MHz on the 1024 MB of GDDR5 memory. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 5770		108 Watts
	Difference: 43 Watts (66%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 5770 is 35% faster than the GeForce GT 640 DDR3 in general, due to its greater bandwidth. (explain)

Radeon HD 5770		76800 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 19776 (35%)

Texel Rate

The Radeon HD 5770 will be a bit (about 18%) more effective at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 5770		34000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 5200 (18%)

Pixel Rate

The GeForce GT 640 DDR3 should be a bit (more or less 6%) more effective at AA than the Radeon HD 5770, and also should be able to handle higher resolutions better. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 5770		13600 Mpixels/sec
	Difference: 800 (6%)

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 largest amount of information (measured in megabytes per second) that can be transported over the external memory interface in one second. It's worked out by multiplying the card's interface width by the speed of its memory. If it uses DDR RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, 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 number of texture map elements (texels) that are applied per second. This figure is calculated by multiplying the total texture units of the card by the core clock 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 processed per second.

Pixel Rate: Pixel rate is the maximum amount 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 worked out by multiplying the amount of Render Output Units by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.