Radeon HD 4870 512MB vs Radeon HD 4890 2GB

Intro

Compare all of that to the Radeon HD 4890 2GB, which features core 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 TAUs 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

The Radeon HD 4890 2GB should theoretically be just a bit faster than the Radeon HD 4870 512MB in general. (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%) better at anisotropic filtering 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 is quite a bit (approximately 33%) faster with regards to anti-aliasing than the Radeon HD 4870 512MB, and also should be capable of handling higher screen resolutions better. (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 data (counted in MB per second) that can be moved over the external memory interface within a second. It is worked out by multiplying the card's bus width by its memory speed. If it uses DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, 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 per second. This is worked out by multiplying the total number of texture units by the core 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 applied in one second.

Pixel Rate: Pixel rate is the most pixels the video card can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.