Radeon HD 4870 1GB vs Radeon HD 6790

Intro

Compare those specifications to the Radeon HD 6790, which features a core clock frequency of 840 MHz and a GDDR5 memory frequency of 1050 MHz. It also features a 256-bit memory bus, and makes use of a 40 nm design. It is comprised of 800 SPUs, 40 TAUs, and 16 Raster Operation Units.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Both cards have the same power consumption.

Memory Bandwidth

The Radeon HD 6790 should theoretically perform a small bit faster than the Radeon HD 4870 1GB overall. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 19200 (17%)

Texel Rate

The Radeon HD 6790 is just a bit (approximately 12%) faster with regards to anisotropic filtering than the Radeon HD 4870 1GB. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 3600 (12%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 6790 is the winner, though not by far. (explain)

Radeon HD 6790		13440 Mpixels/sec
Radeon HD 4870 1GB		12000 Mpixels/sec
	Difference: 1440 (12%)

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: Memory bandwidth is the max amount of data (measured in MB per second) that can be transported across the external memory interface in a second. It's worked out 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 once again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed per second. This is worked out by multiplying the total amount of texture units 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 per 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 amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.