Radeon HD 4850 X2 1GB vs Radeon HD 4890 2GB

Intro

Compare that to the Radeon HD 4890 2GB, which uses a 55 nm design. AMD has set the core speed at 1000 MHz. The GDDR5 memory runs at a frequency of 975 MHz on this card. It features 800(160x5) SPUs as well as 40 TAUs and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4890 2GB		190 Watts
Radeon HD 4850 X2 1GB		250 Watts
	Difference: 60 Watts (32%)

Memory Bandwidth

Performance-wise, the Radeon HD 4850 X2 1GB should in theory be a little bit better than the Radeon HD 4890 2GB in general. (explain)

Radeon HD 4850 X2 1GB		127104 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 2304 (2%)

Texel Rate

The Radeon HD 4850 X2 1GB should be much (approximately 25%) more effective at texture filtering than the Radeon HD 4890 2GB. (explain)

Radeon HD 4850 X2 1GB		50000 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 10000 (25%)

Pixel Rate

The Radeon HD 4850 X2 1GB should be much (about 25%) better at FSAA than the Radeon HD 4890 2GB, and also should be capable of handling higher resolutions while still performing well. (explain)

Radeon HD 4850 X2 1GB		20000 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 4000 (25%)

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.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the maximum amount of information (measured in MB per second) that can be transported across the external memory interface within a second. The number is calculated by multiplying the card's bus width by its memory clock speed. If the card has DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the faster 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 in one second. This is calculated by multiplying the total texture units by the core clock speed of the chip. The higher the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly write to its 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 the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.