Radeon HD 4850 X2 512MB vs Radeon HD 4890 1GB

Intro

Compare those specifications to the Radeon HD 4890 1GB, which uses a 55 nm design. AMD has clocked the core speed at 1000 MHz. The GDDR5 RAM is set to run at a frequency of 975 MHz on this specific 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 1GB		190 Watts
Radeon HD 4850 X2 512MB		250 Watts
	Difference: 60 Watts (32%)

Memory Bandwidth

In theory, the Radeon HD 4850 X2 512MB will be 2% faster than the Radeon HD 4890 1GB overall, because of its greater data rate. (explain)

Radeon HD 4850 X2 512MB		127104 MB/sec
Radeon HD 4890 1GB		124800 MB/sec
	Difference: 2304 (2%)

Texel Rate

The Radeon HD 4850 X2 512MB should be quite a bit (about 25%) more effective at texture filtering than the Radeon HD 4890 1GB. (explain)

Radeon HD 4850 X2 512MB		50000 Mtexels/sec
Radeon HD 4890 1GB		40000 Mtexels/sec
	Difference: 10000 (25%)

Pixel Rate

The Radeon HD 4850 X2 512MB will be much (more or less 25%) more effective at anti-aliasing than the Radeon HD 4890 1GB, and will be capable of handling higher resolutions while still performing well. (explain)

Radeon HD 4850 X2 512MB		20000 Mpixels/sec
Radeon HD 4890 1GB		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 largest amount of information (measured in megabytes per second) that can be transferred across the external memory interface in a second. It's calculated by multiplying the bus width by its memory clock speed. If it uses DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.