GeForce GT 640 DDR3 vs Radeon HD 4850 X2 1GB

Intro

Compare all that to the Radeon HD 4850 X2 1GB, which uses a 55 nm design. AMD has clocked the core speed at 625 MHz. The GDDR3 RAM runs at a frequency of 993 MHz on this particular model. It features 800(160x5) SPUs as well as 40 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 4850 X2 1GB		250 Watts
	Difference: 185 Watts (285%)

Memory Bandwidth

Performance-wise, the Radeon HD 4850 X2 1GB should theoretically be quite a bit superior to the GeForce GT 640 DDR3 in general. (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 should be much (about 74%) better at texture 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

The Radeon HD 4850 X2 1GB should be a lot (about 39%) better at anti-aliasing than the GeForce GT 640 DDR3, and able to handle higher resolutions more effectively. (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: Bandwidth is the largest amount of information (counted in MB per second) that can be transferred past the external memory interface in a second. It's worked out by multiplying the interface width by the speed of its memory. If it uses DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, 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 applied in one second. This figure is worked out by multiplying the total texture units by the core clock speed of the chip. The better this number, the better the 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 most pixels the video card can possibly record to the local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the number of Raster Operations Pipelines by the the card's clock speed. 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 potential to get to the maximum fill rate.