Radeon HD 3870 512MB vs Radeon HD 4830 1GB

Intro

Compare that to the Radeon HD 4830 1GB, which comes with a clock frequency of 575 MHz and a GDDR4 memory frequency of 900 MHz. It also uses a 256-bit bus, and uses a 55 nm design. It is comprised of 640(128x5) SPUs, 32 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4830 1GB		95 Watts
Radeon HD 3870 512MB		106 Watts
	Difference: 11 Watts (12%)

Memory Bandwidth

Both cards have exactly the same memory bandwidth, so in theory they should have identical performance. (explain)

Texel Rate

The Radeon HD 4830 1GB will be quite a bit (approximately 48%) more effective at texture filtering than the Radeon HD 3870 512MB. (explain)

Radeon HD 4830 1GB		18400 Mtexels/sec
Radeon HD 3870 512MB		12400 Mtexels/sec
	Difference: 6000 (48%)

Pixel Rate

The Radeon HD 3870 512MB will be a lot (about 35%) more effective at AA than the Radeon HD 4830 1GB, and also will be capable of handling higher screen resolutions more effectively. (explain)

Radeon HD 3870 512MB		12400 Mpixels/sec
Radeon HD 4830 1GB		9200 Mpixels/sec
	Difference: 3200 (35%)

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 maximum amount of data (measured in MB per second) that can be transferred past the external memory interface in one second. It is worked out by multiplying the card's interface width by the speed of its memory. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied in one second. This figure is calculated by multiplying the total amount of texture units of the card by the core clock 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 applied in a second.

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.