Radeon HD 4790 vs Radeon HD 4870 1GB

Intro

Compare all of that to the Radeon HD 4870 1GB, which comes with a clock speed of 750 MHz and a GDDR5 memory speed of 900 MHz. It also makes use of a 256-bit memory bus, and uses a 55 nm design. It features 800(160x5) SPUs, 40 TAUs, and 16 ROPs.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 4870 1GB will be 13% quicker than the Radeon HD 4790 in general, due to its higher bandwidth. (explain)

Radeon HD 4870 1GB		115200 MB/sec
Radeon HD 4790		102400 MB/sec
	Difference: 12800 (13%)

Texel Rate

The Radeon HD 4870 1GB is quite a bit (about 56%) more effective at texture filtering than the Radeon HD 4790. (explain)

Radeon HD 4870 1GB		30000 Mtexels/sec
Radeon HD 4790		19200 Mtexels/sec
	Difference: 10800 (56%)

Pixel Rate

The Radeon HD 4870 1GB is much (more or less 25%) more effective at full screen anti-aliasing than the Radeon HD 4790, and should be capable of handling higher screen resolutions without losing too much performance. (explain)

Radeon HD 4870 1GB		12000 Mpixels/sec
Radeon HD 4790		9600 Mpixels/sec
	Difference: 2400 (25%)

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 (measured in MB per second) that can be transferred past the external memory interface within a second. The number is calculated by multiplying the card's bus width by its memory clock speed. In the case of DDR type memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher 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 texture map elements (texels) that can be processed in one second. This figure is worked out by multiplying the total number of texture units by the core clock speed of the chip. The higher the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card can possibly record to its local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill 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.