Radeon HD 3870 1GB vs Radeon HD 6990

Intro

Compare all that to the Radeon HD 6990, which comes with a core clock speed of 830 MHz and a GDDR5 memory speed of 1250 MHz. It also features a 256-bit memory bus, and uses a 40 nm design. It is comprised of 1536 SPUs, 96 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 3870 1GB		106 Watts
Radeon HD 6990		375 Watts
	Difference: 269 Watts (254%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6990 will be 344% quicker than the Radeon HD 3870 1GB overall, due to its higher bandwidth. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 3870 1GB		72000 MB/sec
	Difference: 248000 (344%)

Texel Rate

The Radeon HD 6990 will be quite a bit (about 1185%) more effective at AF than the Radeon HD 3870 1GB. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 3870 1GB		12400 Mtexels/sec
	Difference: 146960 (1185%)

Pixel Rate

The Radeon HD 6990 will be quite a bit (about 328%) better at anti-aliasing than the Radeon HD 3870 1GB, and capable of handling higher resolutions without slowing down too much. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 3870 1GB		12400 Mpixels/sec
	Difference: 40720 (328%)

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.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the largest amount of data (counted in MB per second) that can be transferred over the external memory interface in a second. The number is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better 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 amount of texture map elements (texels) that can be processed in one second. This number is calculated by multiplying the total number of texture units by the core clock speed of the chip. The better the texel rate, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly record to its local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the amount of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.