Radeon HD 3850 256MB vs Radeon HD 7990

Intro

Compare all that to the Radeon HD 7990, which has a clock speed of 950 MHz and a GDDR5 memory frequency of 1500 MHz. It also uses a 384-bit memory bus, and makes use of a 28 nm design. It is made up of 2048 SPUs, 128 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 3850 256MB		75 Watts
Radeon HD 7990		375 Watts
	Difference: 300 Watts (400%)

Memory Bandwidth

In theory, the Radeon HD 7990 is 987% faster than the Radeon HD 3850 256MB overall, due to its higher data rate. (explain)

Radeon HD 7990		576000 MB/sec
Radeon HD 3850 256MB		52992 MB/sec
	Difference: 523008 (987%)

Texel Rate

The Radeon HD 7990 will be quite a bit (about 2175%) better at texture filtering than the Radeon HD 3850 256MB. (explain)

Radeon HD 7990		243200 Mtexels/sec
Radeon HD 3850 256MB		10688 Mtexels/sec
	Difference: 232512 (2175%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 7990 is a better choice, by a large margin. (explain)

Radeon HD 7990		60800 Mpixels/sec
Radeon HD 3850 256MB		10688 Mpixels/sec
	Difference: 50112 (469%)

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 max amount of data (in units of MB per second) that can be transferred across the external memory interface in one second. It's worked out by multiplying the bus width by its memory clock speed. If the card has DDR type memory, the result should be multiplied by 2 once again. If 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 per second. This number is worked out by multiplying the total texture units of the card by the core clock speed of the chip. The higher this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the most pixels the graphics card can 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 Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.