Radeon HD 3870 1GB vs Radeon HD 4850 512MB

Intro

Compare those specifications to the Radeon HD 4850 512MB, which has a clock frequency of 625 MHz and a GDDR3 memory frequency of 993 MHz. It also uses a 256-bit memory bus, and uses a 55 nm design. It is made up of 800(160x5) SPUs, 40 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 3870 1GB		106 Watts
Radeon HD 4850 512MB		110 Watts
	Difference: 4 Watts (4%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 3870 1GB should perform a bit faster than the Radeon HD 4850 512MB in general. (explain)

Radeon HD 3870 1GB		72000 MB/sec
Radeon HD 4850 512MB		63552 MB/sec
	Difference: 8448 (13%)

Texel Rate

The Radeon HD 4850 512MB will be much (approximately 102%) better at AF than the Radeon HD 3870 1GB. (explain)

Radeon HD 4850 512MB		25000 Mtexels/sec
Radeon HD 3870 1GB		12400 Mtexels/sec
	Difference: 12600 (102%)

Pixel Rate

If using a high screen resolution is important to you, then the Radeon HD 3870 1GB is the winner, by far. (explain)

Radeon HD 3870 1GB		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: Memory bandwidth is the largest amount of information (in units of megabytes per second) that can be transported across the external memory interface in a second. The number is worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed in one second. This is calculated 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 handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly write to its local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the number 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 drawing the pixels (image) on the screen. The actual pixel fill rate also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.