Radeon HD 4850 X2 512MB vs Radeon HD 4870 X2

Intro

Compare all that to the Radeon HD 4870 X2, which features GPU clock speed of 750 MHz, and 1024 MB of GDDR5 memory set to run at 900 MHz through a 256-bit bus. It also is comprised of 800(160x5) Stream Processors, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4850 X2 512MB		250 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 100 Watts (40%)

Memory Bandwidth

As far as performance goes, the Radeon HD 4870 X2 should theoretically be quite a bit superior to the Radeon HD 4850 X2 512MB overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 4850 X2 512MB		127104 MB/sec
	Difference: 103296 (81%)

Texel Rate

The Radeon HD 4870 X2 should be just a bit (more or less 20%) faster with regards to texture filtering than the Radeon HD 4850 X2 512MB. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 4850 X2 512MB		50000 Mtexels/sec
	Difference: 10000 (20%)

Pixel Rate

The Radeon HD 4870 X2 is just a bit (approximately 20%) more effective at FSAA than the Radeon HD 4850 X2 512MB, and also should be able to handle higher screen resolutions more effectively. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
Radeon HD 4850 X2 512MB		20000 Mpixels/sec
	Difference: 4000 (20%)

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 data (in units of megabytes per second) that can be transferred across the external memory interface within a second. It's calculated by multiplying the bus width by the speed of its memory. If it uses DDR type RAM, it must be multiplied by 2 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 anti-aliasing, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly record to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - aka 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 of the card - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.