Radeon HD 4650 512MB vs Radeon HD 6870

Intro

Compare all of that to the Radeon HD 6870, which uses a 40 nm design. AMD has set the core frequency at 900 MHz. The GDDR5 memory is set to run at a speed of 1050 MHz on this model. It features 1120 SPUs along with 56 Texture Address Units and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 512MB		55 Watts
Radeon HD 6870		151 Watts
	Difference: 96 Watts (175%)

Memory Bandwidth

In theory, the Radeon HD 6870 should perform much faster than the Radeon HD 4650 512MB in general. (explain)

Radeon HD 6870		134400 MB/sec
Radeon HD 4650 512MB		16000 MB/sec
	Difference: 118400 (740%)

Texel Rate

The Radeon HD 6870 should be quite a bit (approximately 163%) better at AF than the Radeon HD 4650 512MB. (explain)

Radeon HD 6870		50400 Mtexels/sec
Radeon HD 4650 512MB		19200 Mtexels/sec
	Difference: 31200 (163%)

Pixel Rate

If using a high screen resolution is important to you, then the Radeon HD 6870 is a better choice, and very much so. (explain)

Radeon HD 6870		28800 Mpixels/sec
Radeon HD 4650 512MB		4800 Mpixels/sec
	Difference: 24000 (500%)

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 (measured in megabytes per second) that can be moved past the external memory interface in a second. It is worked out by multiplying the card's bus width by its memory clock speed. In the case of DDR RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.