Radeon HD 3870 512MB vs Radeon HD 4850 512MB

Intro

Compare those specifications to the Radeon HD 4850 512MB, which comes with a clock speed of 625 MHz and a GDDR3 memory speed of 993 MHz. It also uses a 256-bit memory bus, and uses a 55 nm design. It is comprised of 800(160x5) SPUs, 40 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 3870 512MB		106 Watts
Radeon HD 4850 512MB		110 Watts
	Difference: 4 Watts (4%)

Memory Bandwidth

Theoretically, the Radeon HD 4850 512MB should perform a little bit faster than the Radeon HD 3870 512MB overall. (explain)

Radeon HD 4850 512MB		63552 MB/sec
Radeon HD 3870 512MB		57600 MB/sec
	Difference: 5952 (10%)

Texel Rate

The Radeon HD 4850 512MB will be a lot (about 102%) faster with regards to anisotropic filtering than the Radeon HD 3870 512MB. (explain)

Radeon HD 4850 512MB		25000 Mtexels/sec
Radeon HD 3870 512MB		12400 Mtexels/sec
	Difference: 12600 (102%)

Pixel Rate

The Radeon HD 3870 512MB is a lot (approximately 24%) faster with regards to AA than the Radeon HD 4850 512MB, and also should be able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 3870 512MB		12400 Mpixels/sec
Radeon HD 4850 512MB		10000 Mpixels/sec
	Difference: 2400 (24%)

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: Bandwidth is the max amount of data (in units of MB per second) that can be transferred past the external memory interface in a second. It's calculated by multiplying the interface width by its memory clock speed. In the case of DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly write to the 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 clock speed of the card. 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 lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.