GeForce GT 640 DDR3 vs Radeon HD 4850 X2 512MB

Intro

Compare those specifications to the Radeon HD 4850 X2 512MB, which comes with a core clock speed of 625 MHz and a GDDR3 memory speed of 993 MHz. It also makes use of a 256-bit bus, and makes use of a 55 nm design. It is comprised of 800(160x5) SPUs, 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 512MB		250 Watts
	Difference: 185 Watts (285%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4850 X2 512MB should be much faster than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4850 X2 512MB		127104 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 70080 (123%)

Texel Rate

The Radeon HD 4850 X2 512MB is much (about 74%) faster with regards to AF than the GeForce GT 640 DDR3. (explain)

Radeon HD 4850 X2 512MB		50000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 21200 (74%)

Pixel Rate

If using a high screen resolution is important to you, then the Radeon HD 4850 X2 512MB is a better choice, by far. (explain)

Radeon HD 4850 X2 512MB		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 data (counted in megabytes per second) that can be transferred over the external memory interface within a second. It's calculated by multiplying the card's interface width by its memory speed. If the card has DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly write to its local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.