GeForce GT 640 DDR3 vs Radeon HD 4850 1GB

Intro

Compare those specs to the Radeon HD 4850 1GB, which has a core clock frequency of 625 MHz and a GDDR4 memory speed of 993 MHz. It also uses a 256-bit memory bus, and makes use of a 55 nm design. It features 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 1GB		110 Watts
	Difference: 45 Watts (69%)

Memory Bandwidth

In theory, the Radeon HD 4850 1GB should be 11% quicker than the GeForce GT 640 DDR3 overall, due to its higher bandwidth. (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 should be a little bit (more or less 15%) faster with regards to texture 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

The GeForce GT 640 DDR3 should be much (approximately 44%) better at AA than the Radeon HD 4850 1GB, and should be able to handle higher screen resolutions without slowing down too much. (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 max amount of information (in units of megabytes per second) that can be transferred over the external memory interface in one second. It's calculated by multiplying the card's interface width by the speed of its memory. If it uses DDR type RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This is calculated by multiplying the total amount of texture units by the core 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 applied in one second.

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