GeForce GT 640 DDR3 vs Radeon HD 4850 1GB

Intro

Compare all of 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 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

Theoretically speaking, the Radeon HD 4850 1GB will be 11% faster than the GeForce GT 640 DDR3 in general, because of 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 will be a little bit (approximately 15%) faster with regards to AF 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 a high resolution is important to you, then the GeForce GT 640 DDR3 is a better choice, by a large margin. (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: Memory bandwidth is the largest amount of data (counted in MB per second) that can be transferred past the external memory interface in a second. It's worked out by multiplying the bus width by the speed of its memory. In the case of DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can 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 ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.