Radeon HD 4890 2GB vs Radeon HD 7950 3GB

Intro

Compare those specifications to the Radeon HD 7950 3GB, which features a core clock frequency of 800 MHz and a GDDR5 memory frequency of 1250 MHz. It also features a 384-bit bus, and uses a 28 nm design. It is comprised of 1792 SPUs, 112 TAUs, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4890 2GB		190 Watts
Radeon HD 7950 3GB		200 Watts
	Difference: 10 Watts (5%)

Memory Bandwidth

The Radeon HD 7950 3GB should in theory perform much faster than the Radeon HD 4890 2GB overall. (explain)

Radeon HD 7950 3GB		240000 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 115200 (92%)

Texel Rate

The Radeon HD 7950 3GB will be a lot (more or less 124%) faster with regards to texture filtering than the Radeon HD 4890 2GB. (explain)

Radeon HD 7950 3GB		89600 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 49600 (124%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 7950 3GB is a better choice, by far. (explain)

Radeon HD 7950 3GB		25600 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 9600 (60%)

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 (counted in MB per second) that can be transported over the external memory interface in a second. It's calculated by multiplying the card's interface width by its memory speed. In the case of DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are applied in one second. This number is worked out by multiplying the total 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 applied per second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly write to its local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.