Radeon HD 4870 1GB vs Radeon HD 4890 2GB

Intro

Compare those specifications to the Radeon HD 4890 2GB, which has a GPU core clock speed of 1000 MHz, and 2048 MB of GDDR5 RAM set to run at 975 MHz through a 256-bit bus. It also features 800(160x5) Stream Processors, 40 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 1GB		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 1GB in general, due to its higher bandwidth. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 9600 (8%)

Texel Rate

The Radeon HD 4890 2GB will be much (more or less 33%) better at AF than the Radeon HD 4870 1GB. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 10000 (33%)

Pixel Rate

The Radeon HD 4890 2GB should be a lot (about 33%) more effective at AA than the Radeon HD 4870 1GB, and able to handle higher screen resolutions while still performing well. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 4870 1GB		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 largest amount of information (in units of MB per second) that can be transferred over the external memory interface in one second. The number is calculated by multiplying the card's interface width by the speed of its memory. If it uses DDR type RAM, it must be multiplied by 2 once again. If 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, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed in one second. This is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The higher this number, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the most pixels that the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.