Radeon HD 4850 512MB vs Radeon HD 4870 1GB

Intro

Compare all of that to the Radeon HD 4870 1GB, which features core clock speeds of 750 MHz on the GPU, and 900 MHz on the 1024 MB of GDDR5 memory. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4850 512MB		110 Watts
Radeon HD 4870 1GB		150 Watts
	Difference: 40 Watts (36%)

Memory Bandwidth

Performance-wise, the Radeon HD 4870 1GB should in theory be much superior to the Radeon HD 4850 512MB overall. (explain)

Radeon HD 4870 1GB		115200 MB/sec
Radeon HD 4850 512MB		63552 MB/sec
	Difference: 51648 (81%)

Texel Rate

The Radeon HD 4870 1GB should be just a bit (about 20%) faster with regards to texture filtering than the Radeon HD 4850 512MB. (explain)

Radeon HD 4870 1GB		30000 Mtexels/sec
Radeon HD 4850 512MB		25000 Mtexels/sec
	Difference: 5000 (20%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 4870 1GB is superior to the Radeon HD 4850 512MB, but not by far. (explain)

Radeon HD 4870 1GB		12000 Mpixels/sec
Radeon HD 4850 512MB		10000 Mpixels/sec
	Difference: 2000 (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.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the maximum amount of data (in units of MB per second) that can be moved over the external memory interface in one second. The number is calculated by multiplying the bus width by its memory clock speed. If the card has DDR type RAM, the result should be multiplied by 2 once again. If it uses 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 high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied per second. This is calculated by multiplying the total amount of texture units by the core speed of the chip. The higher the texel rate, the better the video 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 could possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.