Radeon HD 4650 1GB vs Radeon HD 6790

Intro

Compare those specifications to the Radeon HD 6790, which comes with core clock speeds of 840 MHz on the GPU, and 1050 MHz on the 1024 MB of GDDR5 RAM. It features 800 SPUs along with 40 Texture Address Units and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 1GB		55 Watts
Radeon HD 6790		150 Watts
	Difference: 95 Watts (173%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6790 will be 500% faster than the Radeon HD 4650 1GB overall, because of its greater data rate. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4650 1GB		22400 MB/sec
	Difference: 112000 (500%)

Texel Rate

The Radeon HD 6790 should be much (approximately 75%) more effective at anisotropic filtering than the Radeon HD 4650 1GB. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 4650 1GB		19200 Mtexels/sec
	Difference: 14400 (75%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 6790 is a better choice, by a large margin. (explain)

Radeon HD 6790		13440 Mpixels/sec
Radeon HD 4650 1GB		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: Memory bandwidth is the max amount of data (measured in megabytes per second) that can be transferred over the external memory interface within a second. The number is worked out by multiplying the card's interface width by the speed of its memory. If it uses DDR type RAM, it must be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly record to its local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also called 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 - the lower the bandwidth is, the lower the ability to get to the max fill rate.