GeForce GT 640 DDR3 vs Radeon HD 4850 512MB

Intro

Compare those specifications to the Radeon HD 4850 512MB, which has GPU clock speed of 625 MHz, and 512 MB of GDDR3 memory set to run at 993 MHz through a 256-bit bus. It also is comprised of 800(160x5) Stream Processors, 40 Texture Address Units, 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 512MB		110 Watts
	Difference: 45 Watts (69%)

Memory Bandwidth

The Radeon HD 4850 512MB, in theory, should be a bit faster than the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 4850 512MB		63552 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 6528 (11%)

Texel Rate

The GeForce GT 640 DDR3 should be a bit (more or less 15%) more effective at AF than the Radeon HD 4850 512MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4850 512MB		25000 Mtexels/sec
	Difference: 3800 (15%)

Pixel Rate

The GeForce GT 640 DDR3 should be quite a bit (about 44%) more effective at AA than the Radeon HD 4850 512MB, and should be able to handle higher screen resolutions without losing too much performance. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4850 512MB		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: Memory bandwidth is the max amount of information (measured in megabytes per second) that can be transported past the external memory interface within a second. It's calculated by multiplying the card's bus width by its memory speed. If the card has DDR type memory, it should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the number of colour ROPs by the clock speed of the card. 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 output rate is also dependant on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.