Radeon HD 4790 vs Radeon HD 4870 X2

Intro

Compare that to the Radeon HD 4870 X2, which has a clock speed of 750 MHz and a GDDR5 memory frequency of 900 MHz. It also makes use of a 256-bit memory bus, and uses a 55 nm design. It is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 4870 X2 should perform much faster than the Radeon HD 4790 overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 4790		102400 MB/sec
	Difference: 128000 (125%)

Texel Rate

The Radeon HD 4870 X2 is a lot (approximately 213%) more effective at texture filtering than the Radeon HD 4790. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 4790		19200 Mtexels/sec
	Difference: 40800 (213%)

Pixel Rate

The Radeon HD 4870 X2 will be quite a bit (approximately 150%) more effective at anti-aliasing than the Radeon HD 4790, and also will be able to handle higher screen resolutions without slowing down too much. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
Radeon HD 4790		9600 Mpixels/sec
	Difference: 14400 (150%)

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 information (measured in MB per second) that can be transferred past the external memory interface within a second. It is worked out by multiplying the card's interface width by the speed of its memory. If the card has DDR memory, it should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

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