GeForce GT 640 DDR3 vs Radeon HD 6770 1GB

Intro

Compare that to the Radeon HD 6770 1GB, which comes with a core clock frequency of 900 MHz and a GDDR5 memory frequency of 1050 MHz. It also uses a 128-bit memory bus, and makes use of a 40 nm design. It features 800 SPUs, 40 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 6770 1GB		108 Watts
	Difference: 43 Watts (66%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6770 1GB will be 18% quicker than the GeForce GT 640 DDR3 in general, due to its greater bandwidth. (explain)

Radeon HD 6770 1GB		67200 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 10176 (18%)

Texel Rate

The Radeon HD 6770 1GB should be a lot (more or less 25%) more effective at AF than the GeForce GT 640 DDR3. (explain)

Radeon HD 6770 1GB		36000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 7200 (25%)

Pixel Rate

Both cards have exactly the same pixel rate, so in theory they should perform equally good at at anti-aliasing, and be capable of handling the same screen resolutions. (explain)

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 max amount of information (in units of MB per second) that can be moved past the external memory interface in one second. The number is worked out by multiplying the interface width by the speed of its memory. In the case of DDR RAM, it must be multiplied by 2 again. If 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 are processed per second. This 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 graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount 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 drawing the pixels (image) on the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.