Radeon HD 4870 2GB vs Radeon HD 7790

Intro

Compare those specifications to the Radeon HD 7790, which comes with a clock frequency of 1000 MHz and a GDDR5 memory frequency of 1500 MHz. It also features a 128-bit memory bus, and uses a 28 nm design. It features 896 SPUs, 56 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7790		85 Watts
Radeon HD 4870 2GB		150 Watts
	Difference: 65 Watts (76%)

Memory Bandwidth

In theory, the Radeon HD 4870 2GB will be 20% faster than the Radeon HD 7790 in general, due to its higher bandwidth. (explain)

Radeon HD 4870 2GB		115200 MB/sec
Radeon HD 7790		96000 MB/sec
	Difference: 19200 (20%)

Texel Rate

The Radeon HD 7790 is quite a bit (approximately 87%) faster with regards to texture filtering than the Radeon HD 4870 2GB. (explain)

Radeon HD 7790		56000 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 26000 (87%)

Pixel Rate

The Radeon HD 7790 should be quite a bit (approximately 33%) more effective at FSAA than the Radeon HD 4870 2GB, and also will be capable of handling higher screen resolutions while still performing well. (explain)

Radeon HD 7790		16000 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 4000 (33%)

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 largest amount of information (counted in megabytes per second) that can be moved over the external memory interface in one second. It is calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR RAM, 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, High Dynamic Range and higher screen 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 by the core clock speed of the chip. The higher the texel rate, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a 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. Pixel rate is calculated by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.