Radeon HD 4770 vs Radeon HD 6790

Intro

Compare that to the Radeon HD 6790, which makes use of a 40 nm design. AMD has set the core frequency at 840 MHz. The GDDR5 RAM runs at a frequency of 1050 MHz on this model. It features 800 SPUs as well as 40 TAUs and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4770		80 Watts
Radeon HD 6790		150 Watts
	Difference: 70 Watts (88%)

Memory Bandwidth

The Radeon HD 6790 should in theory perform much faster than the Radeon HD 4770 in general. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4770		51200 MB/sec
	Difference: 83200 (163%)

Texel Rate

The Radeon HD 6790 will be quite a bit (approximately 40%) more effective at AF than the Radeon HD 4770. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 4770		24000 Mtexels/sec
	Difference: 9600 (40%)

Pixel Rate

The Radeon HD 6790 is just a bit (approximately 12%) more effective at AA than the Radeon HD 4770, and should be able to handle higher resolutions while still performing well. (explain)

Radeon HD 6790		13440 Mpixels/sec
Radeon HD 4770		12000 Mpixels/sec
	Difference: 1440 (12%)

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 (measured in MB per second) that can be moved over the external memory interface within a second. The number is worked out by multiplying the interface width by its memory speed. If the card has DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This number is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The higher the texel rate, 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 number of pixels that the graphics chip can possibly write to its local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the number of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.