Radeon HD 4650 1GB vs Radeon HD 6850

Intro

Compare that to the Radeon HD 6850, which features GPU clock speed of 775 MHz, and 1024 MB of GDDR5 RAM set to run at 1000 MHz through a 256-bit bus. It also is made up of 960 Stream Processors, 48 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 1GB		55 Watts
Radeon HD 6850		127 Watts
	Difference: 72 Watts (131%)

Memory Bandwidth

Performance-wise, the Radeon HD 6850 should in theory be quite a bit better than the Radeon HD 4650 1GB in general. (explain)

Radeon HD 6850		128000 MB/sec
Radeon HD 4650 1GB		22400 MB/sec
	Difference: 105600 (471%)

Texel Rate

The Radeon HD 6850 is quite a bit (about 94%) faster with regards to anisotropic filtering than the Radeon HD 4650 1GB. (explain)

Radeon HD 6850		37200 Mtexels/sec
Radeon HD 4650 1GB		19200 Mtexels/sec
	Difference: 18000 (94%)

Pixel Rate

The Radeon HD 6850 will be quite a bit (more or less 417%) more effective at full screen anti-aliasing than the Radeon HD 4650 1GB, and also will be able to handle higher screen resolutions without losing too much performance. (explain)

Radeon HD 6850		24800 Mpixels/sec
Radeon HD 4650 1GB		4800 Mpixels/sec
	Difference: 20000 (417%)

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 largest amount of information (measured in MB per second) that can be transferred over the external memory interface in a second. It is worked out by multiplying the interface width by its memory clock speed. In the case of DDR RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, 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 number of texture map elements (texels) that are applied per second. This number is worked out by multiplying the total number of texture units by the core speed of the chip. The better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card can possibly record to its local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the number of 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 fill rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.