Articles: Graphics

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AMD’s newest graphics cards based on the Pitcairn GPU of the Southern Islands family, namely Radeon HD 7870 GHz Edition and Radeon HD 7850, were officially unveiled about a month ago, but it’s only now that they can be found in shops. These are performance-mainstream solutions priced at $349 and $249, respectively. AMD suggests that your gaming can only be serious if you’ve got one of these products.

This implies that any graphics card from a lower class is not really meant for gamers. Well, this is an arguable point because it doesn’t agree with the fact that PC video games have not been very demanding in their system requirements lately, with but a few exception.

We are going to check out the new graphics cards with their Pitcairn GPUs that feature AMD’s Graphics Core Next microarchitecture and will compare their performance with same-class opponents.

Architecture and Positioning

Right now, AMD’s Southern Islands family is comprised of the Tahiti, Pitcairn and Cape Verde GPUs which are designed for top-end, midrange and low-end graphics cards, respectively.

We’re already acquainted with the Tahiti-based Radeon HD 7970 and HD 7950 cards, so now we want to take a look at the Pitcairn which features the same Graphics Core Next microarchitecture.

From a functional standpoint, the Pitcairn is no different from the Tahiti but has fewer unified shader processors (1280 and 1024 in the HD 7870 and HD 7850 as opposed to the HD 7950’s 1792) and fewer texture-mapping units (80 and 64 as compared to 112, respectively). The number of raster operators has remained the same at 32. Therefore the amount of transistors is reduced from 4313 to 2800 million whereas the die size is 212 rather than 365 sq. millimeters. That’s about all as to the architectural differences between the Pitcairn and the Tahiti.

Compared to its predecessors, the Radeon HD 7870 is up to 4.25 times as fast as the Radeon HD 6970 and also much faster than the GeForce GTX 570 and even GTX 580 in tessellation-heavy applications.

Besides the abovementioned architectural differences, the $100 gap between the Radeon HD 7870 and HD 7850 in recommended price is also due to their GPU clock rates: 1000 MHz for the HD 7870 and 860 MHz for the HD 7850.


The HD 7850 is likely to be made out of GPUs that couldn’t be used for the HD 7870, so we can’t expect it to be very good at overclocking. However, AMD claims that the new graphics cards are both overclocker-friendly.


Energy efficiency being a hot topic nowadays, the typical power consumption of the Radeon HD 7870 is specified to be 175 watts (and up to 190 watts under peak load) whereas the HD 7850 consumes 130 watts (up to 150 watts under peak load). This is lower compared to the Radeon HD 6970’s 250 watts. The new cards need no more than 20 watts when idle and require a mere 3 watts when the monitor is turned off.

There’s nothing unusual about the new cards’ market positioning. Considering the price factor, the Radeon HD 7850 is supposed to compete with Nvidia’s GeForce GTX 560 Ti and GTX 570 whereas the Radeon HD 7870 is somewhere in between the GeForce GTX 570 and GTX 580.

It’s somewhat different in practice, though, as you will learn shortly.

The new cards support morphological antialiasing version 2.0…

…and sparse grid supersample antialiasing which offers the highest image quality:

We don’t know if the Radeon HD 7870 and HD 7850 support the new antialiasing algorithms FXAA and TXAA.

The new cards’ specs are listed in the table in comparison with AMD’s Radeon HD 7950, Radeon HD 6970 and Radeon HD 6870:

* - may vary for each particular graphics card unit.

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