GeForce GT 640 DDR3 vs Radeon HD 4850 X2 1GB

Intro

Compare all of that to the Radeon HD 4850 X2 1GB, which comes with GPU clock speed of 625 MHz, and 1024 MB of GDDR3 memory set to run at 993 MHz through a 256-bit bus. It also features 800(160x5) Stream Processors, 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 4850 X2 1GB		250 Watts
	Difference: 185 Watts (285%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4850 X2 1GB should be a lot faster than 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 quite a bit (approximately 74%) faster with regards to AF 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 will be a lot (more or less 39%) better at full screen anti-aliasing than the GeForce GT 640 DDR3, and should be capable of handling higher resolutions while still performing well. (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 maximum amount of information (measured in megabytes per second) that can be moved over the external memory interface in a second. It's calculated by multiplying the bus width by the speed of its memory. If the card has DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the the core clock speed. 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 also depends on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.