Radeon HD 4650 512MB vs Radeon HD 6790

Intro

Compare that to the Radeon HD 6790, which has GPU clock speed of 840 MHz, and 1024 MB of GDDR5 RAM set to run at 1050 MHz through a 256-bit bus. It also is made up of 800 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 512MB		55 Watts
Radeon HD 6790		150 Watts
	Difference: 95 Watts (173%)

Memory Bandwidth

Theoretically, the Radeon HD 6790 should be quite a bit faster than the Radeon HD 4650 512MB in general. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4650 512MB		16000 MB/sec
	Difference: 118400 (740%)

Texel Rate

The Radeon HD 6790 should be quite a bit (more or less 75%) better at AF than the Radeon HD 4650 512MB. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 4650 512MB		19200 Mtexels/sec
	Difference: 14400 (75%)

Pixel Rate

The Radeon HD 6790 is quite a bit (approximately 180%) better at AA than the Radeon HD 4650 512MB, and also able to handle higher resolutions while still performing well. (explain)

Radeon HD 6790		13440 Mpixels/sec
Radeon HD 4650 512MB		4800 Mpixels/sec
	Difference: 8640 (180%)

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 across the external memory interface in a second. It's worked out by multiplying the bus width by its memory speed. If the card has DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This figure is worked out by multiplying the total texture units of the card 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 processed per 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 figure is calculated by multiplying the number of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.