Radeon HD 4870 512MB vs Radeon HD 4890 2GB

Intro

Compare all of that to the Radeon HD 4890 2GB, which comes with core speeds of 1000 MHz on the GPU, and 975 MHz on the 2048 MB of GDDR5 memory. It features 800(160x5) SPUs as well as 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 512MB		150 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 40 Watts (27%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4890 2GB should be 8% quicker than the Radeon HD 4870 512MB in general, because of its greater bandwidth. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 4870 512MB		115200 MB/sec
	Difference: 9600 (8%)

Texel Rate

The Radeon HD 4890 2GB should be quite a bit (more or less 33%) more effective at AF than the Radeon HD 4870 512MB. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 4870 512MB		30000 Mtexels/sec
	Difference: 10000 (33%)

Pixel Rate

The Radeon HD 4890 2GB should be quite a bit (approximately 33%) more effective at full screen anti-aliasing than the Radeon HD 4870 512MB, and should be able to handle higher screen resolutions without losing too much performance. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 4870 512MB		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: Bandwidth is the maximum amount of information (measured in MB per second) that can be transported 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 memory, it should be multiplied by 2 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, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one 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 this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the video 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 amount of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.