GeForce GT 640 DDR3 vs Radeon HD 4850 X2 1GB

Intro

Compare those specifications to the Radeon HD 4850 X2 1GB, which comes with a core clock speed of 625 MHz and a GDDR3 memory speed of 993 MHz. It also features a 256-bit memory bus, and uses a 55 nm design. It features 800(160x5) SPUs, 40 Texture Address Units, 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 4850 X2 1GB		250 Watts
	Difference: 185 Watts (285%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4850 X2 1GB is 123% faster than the GeForce GT 640 DDR3 overall, due to its higher bandwidth. (explain)

Radeon HD 4850 X2 1GB		127104 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 70080 (123%)

Texel Rate

The Radeon HD 4850 X2 1GB is much (about 74%) better at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 4850 X2 1GB		50000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 21200 (74%)

Pixel Rate

If running with high levels of AA is important to you, then the Radeon HD 4850 X2 1GB is a better choice, by far. (explain)

Radeon HD 4850 X2 1GB		20000 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 5600 (39%)

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.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the maximum amount of data (in units of MB per second) that can be transferred past the external memory interface in a second. The number is calculated by multiplying the bus width by the speed of its memory. If it uses DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly record to the local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the amount of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.