Radeon HD 4850 2GB vs Radeon HD 6870

Intro

Compare those specifications to the Radeon HD 6870, which comes with a clock frequency of 900 MHz and a GDDR5 memory frequency of 1050 MHz. It also features a 256-bit memory bus, and uses a 40 nm design. It features 1120 SPUs, 56 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4850 2GB		110 Watts
Radeon HD 6870		151 Watts
	Difference: 41 Watts (37%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6870 should be 111% faster than the Radeon HD 4850 2GB overall, because of its greater data rate. (explain)

Radeon HD 6870		134400 MB/sec
Radeon HD 4850 2GB		63552 MB/sec
	Difference: 70848 (111%)

Texel Rate

The Radeon HD 6870 is quite a bit (more or less 102%) better at texture filtering than the Radeon HD 4850 2GB. (explain)

Radeon HD 6870		50400 Mtexels/sec
Radeon HD 4850 2GB		25000 Mtexels/sec
	Difference: 25400 (102%)

Pixel Rate

The Radeon HD 6870 is quite a bit (more or less 188%) better at FSAA than the Radeon HD 4850 2GB, and should be able to handle higher screen resolutions while still performing well. (explain)

Radeon HD 6870		28800 Mpixels/sec
Radeon HD 4850 2GB		10000 Mpixels/sec
	Difference: 18800 (188%)

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 transported over the external memory interface in one second. It is worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR type memory, it should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better 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 texture map elements (texels) that are processed per second. This figure is calculated by multiplying the total texture units by the core speed of the chip. The higher the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the most pixels the video card could possibly record to its local memory per second - measured in millions of pixels per second. Pixel rate 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 outputting the pixels (image) to the screen. The actual pixel rate is also dependant on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.