Radeon HD 4850 X2 512MB vs Radeon HD 4870 2GB

Intro

Compare those specs to the Radeon HD 4870 2GB, which features core clock speeds of 750 MHz on the GPU, and 900 MHz on the 2048 MB of GDDR5 RAM. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 2GB		150 Watts
Radeon HD 4850 X2 512MB		250 Watts
	Difference: 100 Watts (67%)

Memory Bandwidth

Performance-wise, the Radeon HD 4850 X2 512MB should theoretically be a small bit better than the Radeon HD 4870 2GB overall. (explain)

Radeon HD 4850 X2 512MB		127104 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 11904 (10%)

Texel Rate

The Radeon HD 4850 X2 512MB should be much (more or less 67%) faster with regards to texture filtering than the Radeon HD 4870 2GB. (explain)

Radeon HD 4850 X2 512MB		50000 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 20000 (67%)

Pixel Rate

The Radeon HD 4850 X2 512MB will be much (about 67%) better at AA than the Radeon HD 4870 2GB, and will be capable of handling higher screen resolutions better. (explain)

Radeon HD 4850 X2 512MB		20000 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 8000 (67%)

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 MB per second) that can be transferred over the external memory interface in one second. It is worked out by multiplying the bus width by its memory clock speed. If it uses DDR memory, 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 AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the video card could possibly record to its local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the number of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.