Radeon HD 4870 2GB vs Radeon HD 4890 2GB

Intro

Compare all that to the Radeon HD 4890 2GB, which comes with clock speeds of 1000 MHz on the GPU, and 975 MHz on the 2048 MB of GDDR5 RAM. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 2GB		150 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 40 Watts (27%)

Memory Bandwidth

Theoretically, the Radeon HD 4890 2GB should perform a small bit faster than the Radeon HD 4870 2GB overall. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 9600 (8%)

Texel Rate

The Radeon HD 4890 2GB should be much (more or less 33%) faster with regards to texture filtering than the Radeon HD 4870 2GB. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 10000 (33%)

Pixel Rate

The Radeon HD 4890 2GB should be much (more or less 33%) better at FSAA than the Radeon HD 4870 2GB, and also will be capable of handling higher resolutions while still performing well. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 4000 (33%)

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 max amount of data (measured in megabytes per second) that can be moved over the external memory interface in a second. The number is worked out by multiplying the card's bus width by its memory speed. In the case of DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the card's memory bandwidth, the better 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 amount of texture map elements (texels) that are processed per second. This is calculated by multiplying the total amount of texture units of the card by the core clock 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 that the graphics chip could possibly write to the 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 drawing the pixels (image) on the screen. The actual pixel fill rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.