Radeon HD 4870 512MB vs Radeon HD 6790

Intro

Compare all of that to the Radeon HD 6790, which uses a 40 nm design. AMD has set the core speed at 840 MHz. The GDDR5 RAM is set to run at a frequency of 1050 MHz on this specific card. It features 800 SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Both cards have the same power consumption.

Memory Bandwidth

Theoretically speaking, the Radeon HD 6790 is 17% faster than the Radeon HD 4870 512MB in general, because of its higher bandwidth. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4870 512MB		115200 MB/sec
	Difference: 19200 (17%)

Texel Rate

The Radeon HD 6790 should be just a bit (approximately 12%) more effective at AF than the Radeon HD 4870 512MB. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 4870 512MB		30000 Mtexels/sec
	Difference: 3600 (12%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 6790 is a better choice, but it probably won't make a huge difference. (explain)

Radeon HD 6790		13440 Mpixels/sec
Radeon HD 4870 512MB		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: Bandwidth is the largest amount of data (measured in megabytes per second) that can be transported across the external memory interface within a second. It's calculated by multiplying the interface width by its memory speed. If it uses DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, 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 number of texture map elements (texels) that can be processed in one second. This figure is calculated by multiplying the total number of texture units by the core speed of the chip. The better the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card 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 - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.