GeForce GT 640 DDR3 vs Radeon R9 M275X

Intro

Compare all of that to the Radeon R9 M275X, which uses a 28 nm design. AMD has clocked the core speed at 900 MHz. The GDDR5 memory runs at a frequency of 1125 MHz on this specific model. It features 640 SPUs along with 40 Texture Address Units and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon R9 M275X		50 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 15 Watts (30%)

Memory Bandwidth

Performance-wise, the Radeon R9 M275X should in theory be quite a bit better than the GeForce GT 640 DDR3 in general. (explain)

Radeon R9 M275X		72000 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 14976 (26%)

Texel Rate

The Radeon R9 M275X will be much (more or less 25%) better at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

Radeon R9 M275X		36000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 7200 (25%)

Pixel Rate

Both cards have the exact same pixel rate, so in theory they should be equally good at at AA, and be able to handle 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: Memory bandwidth is the largest amount of information (counted in megabytes per second) that can be transported past the external memory interface within a second. The number is worked out by multiplying the card's bus width by its memory clock speed. If the card has DDR type memory, the result should be multiplied by 2 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 AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied per second. This figure is worked out by multiplying the total texture units by the core speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly record to its local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of colour ROPs by the clock speed of the card. 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 many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the max fill rate.