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

Intro

Compare those specs to the Radeon HD 4890 2GB, which has a clock frequency of 1000 MHz and a GDDR5 memory speed of 975 MHz. It also uses a 256-bit memory bus, and uses a 55 nm design. It is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 ROPs.

(No game benchmarks for this combination yet.)

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 theoretically be just a 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 will be quite a bit (more or less 25%) faster with regards to 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

If running with a high screen resolution is important to you, then the Radeon HD 4850 X2 1GB is a better choice, and very much so. (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 max amount of information (in units of megabytes per second) that can be transported past the external memory interface in one second. It's worked out by multiplying the card's bus width by its memory speed. In the case of DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher 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 figure is calculated 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 card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the the card's 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 lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.