Radeon HD 4790 vs Radeon HD 4890 2GB

Intro

Compare those specifications to the Radeon HD 4890 2GB, which uses a 55 nm design. ATi has set the core frequency at 1000 MHz. The GDDR5 RAM is set to run at a frequency of 975 MHz on this specific model. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 4890 2GB should be much faster than the Radeon HD 4790 in general. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 4790		102400 MB/sec
	Difference: 22400 (22%)

Texel Rate

The Radeon HD 4890 2GB should be quite a bit (about 108%) better at anisotropic filtering than the Radeon HD 4790. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 4790		19200 Mtexels/sec
	Difference: 20800 (108%)

Pixel Rate

The Radeon HD 4890 2GB will be quite a bit (more or less 67%) better at AA than the Radeon HD 4790, and also should be capable of handling higher resolutions better. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 4790		9600 Mpixels/sec
	Difference: 6400 (67%)

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 max amount of information (in units of megabytes per second) that can be transported past the external memory interface in a second. It's worked out by multiplying the bus width by its memory speed. In the case of DDR type memory, the result should 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, High Dynamic Range and high 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 texture units of the card by the core clock speed of the chip. The better the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.

Pixel Rate: Pixel rate is the maximum amount of pixels the video card could possibly record to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of ROPs 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 rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.