Radeon HD 4870 512MB vs Radeon HD 6790

Intro

Compare all of that to the Radeon HD 6790, which has a clock frequency of 840 MHz and a GDDR5 memory speed of 1050 MHz. It also makes use of a 256-bit memory bus, and makes use of a 40 nm design. It is comprised of 800 SPUs, 40 TAUs, and 16 ROPs.

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 should perform a small bit faster than the Radeon HD 4870 512MB in general. (explain)

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

Texel Rate

The Radeon HD 6790 will be a bit (about 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

The Radeon HD 6790 is just a bit (about 12%) faster with regards to AA than the Radeon HD 4870 512MB, and also should be able to handle higher resolutions more effectively. (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 maximum amount of information (in units of megabytes per second) that can be transported past the external memory interface in one second. The number is calculated by multiplying the bus width by its memory speed. If the card has DDR type RAM, it should be multiplied by 2 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, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The higher the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the number of colour ROPs by the the core 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 also depends 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.