Radeon HD 4870 2GB vs Radeon HD 7870

Intro

Compare those specifications to the Radeon HD 7870, which has clock speeds of 1000 MHz on the GPU, and 1200 MHz on the 2048 MB of GDDR5 RAM. It features 1280 SPUs along with 80 Texture Address Units and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 2GB		150 Watts
Radeon HD 7870		175 Watts
	Difference: 25 Watts (17%)

Memory Bandwidth

The Radeon HD 7870, in theory, should be much faster than the Radeon HD 4870 2GB in general. (explain)

Radeon HD 7870		153600 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 38400 (33%)

Texel Rate

The Radeon HD 7870 should be quite a bit (about 167%) more effective at texture filtering than the Radeon HD 4870 2GB. (explain)

Radeon HD 7870		80000 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 50000 (167%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 7870 is the winner, by a large margin. (explain)

Radeon HD 7870		32000 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 20000 (167%)

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 information (in units of megabytes per second) that can be moved past the external memory interface in one second. The number is calculated by multiplying the bus width by its memory clock speed. If the card has DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's 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 are applied in one second. This figure is worked out by multiplying the total number of texture units by the core clock speed of the chip. The better the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly record to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Render Output Units by the the card's clock speed. 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 output rate is also dependant on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.