GeForce GT 640 DDR3 vs Radeon HD 4850 1GB

Intro

Compare all that to the Radeon HD 4850 1GB, which comes with clock speeds of 625 MHz on the GPU, and 993 MHz on the 1024 MB of GDDR4 RAM. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator 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 1GB		110 Watts
	Difference: 45 Watts (69%)

Memory Bandwidth

The Radeon HD 4850 1GB should in theory be a little bit faster than the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 4850 1GB		63552 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 6528 (11%)

Texel Rate

The GeForce GT 640 DDR3 is just a bit (about 15%) faster with regards to anisotropic filtering than the Radeon HD 4850 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4850 1GB		25000 Mtexels/sec
	Difference: 3800 (15%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is superior to the Radeon HD 4850 1GB, and very much so. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4850 1GB		10000 Mpixels/sec
	Difference: 4400 (44%)

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: Bandwidth is the maximum amount of data (in units of megabytes per second) that can be transferred past the external memory interface in a second. It's worked out by multiplying the interface width by its memory speed. If the card has DDR type RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed 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 video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of Render Output Units 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 many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.