Radeon HD 4870 1GB vs Radeon HD 6790

Intro

Compare that to the Radeon HD 6790, which has a core clock frequency of 840 MHz and a GDDR5 memory speed of 1050 MHz. It also uses a 256-bit memory bus, and uses a 40 nm design. It is made up 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 is 17% quicker than the Radeon HD 4870 1GB in general, due to its higher bandwidth. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 19200 (17%)

Texel Rate

The Radeon HD 6790 will be a little bit (about 12%) better at anisotropic filtering than the Radeon HD 4870 1GB. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 3600 (12%)

Pixel Rate

The Radeon HD 6790 will be a little bit (more or less 12%) faster with regards to AA than the Radeon HD 4870 1GB, and will be capable of handling higher resolutions while still performing well. (explain)

Radeon HD 6790		13440 Mpixels/sec
Radeon HD 4870 1GB		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 (in units of MB per second) that can be moved past the external memory interface within a second. The number is calculated by multiplying the card's bus width by its memory speed. If it uses DDR RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This figure is calculated by multiplying the total amount of texture units by the core clock 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 processed per second.

Pixel Rate: Pixel rate is the most pixels the video card could possibly write to the local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the number of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.