Radeon HD 4650 512MB vs Radeon HD 6790

Intro

Compare those specifications to the Radeon HD 6790, which has a clock speed of 840 MHz and a GDDR5 memory frequency of 1050 MHz. It also uses a 256-bit memory bus, and makes use of a 40 nm design. It is made up of 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

Theoretically, the Radeon HD 6790 should be a lot 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%) 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 running with a high screen resolution is important to you, then the Radeon HD 6790 is superior to the Radeon HD 4650 512MB, and very much so. (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 max amount of information (in units of megabytes per second) that can be moved past the external memory interface in one second. It is calculated by multiplying the interface width by its memory speed. If it uses DDR type RAM, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR 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 worked out by multiplying the total amount of texture units of the card by the core speed of the chip. The higher this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip can possibly write to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.