Radeon HD 4650 512MB vs Radeon HD 6790

Intro

Compare those specifications to the Radeon HD 6790, which features a clock speed of 840 MHz and a GDDR5 memory speed of 1050 MHz. It also features a 256-bit bus, and uses a 40 nm design. It features 800 SPUs, 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 512MB		55 Watts
Radeon HD 6790		150 Watts
	Difference: 95 Watts (173%)

Memory Bandwidth

As far as performance goes, the Radeon HD 6790 should in theory be much superior to the Radeon HD 4650 512MB overall. (explain)

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

Texel Rate

The Radeon HD 6790 is quite a bit (approximately 75%) faster with regards to texture filtering 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

If using a high screen resolution is important to you, then the Radeon HD 6790 is the winner, by far. (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: Memory bandwidth is the largest amount of data (counted in megabytes per second) that can be moved across the external memory interface in one second. It is worked out by multiplying the card's bus width by the speed of its memory. In the case of DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster 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 processed per second. This is worked out by multiplying the total texture units by the core speed of the chip. The higher the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of colour ROPs by the the core clock speed. 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 rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.