Review: AMD Radeon HD 7870 and HD 7850 graphics cards

HEXUS.bang4buck and bang4watt

Putting all the numbers into perspective, let's take a closer look at overall performance and value for money.

In a rough-and-ready assessment of the cards' bang for buck, we've aggregated the frame-rates for all our gaming benchmarks, normalised them¹ and taken account of today's pricing.

But there are more provisos than we'd care to shake a stick at. We could have chosen different games, the cards' prices could have been derived from other sources, and pricing tends to fluctuate daily, especially for new-release GPUs.

Consequently, the tables below highlight a metric that should only be used as a yardstick for evaluating comparative performance with price factored in.

¹ the normalisation refers to taking playable frame rate into account. Should a card benchmark at over 60 frames per second in any one game, the extra fps count as half. Similarly, should a card benchmark lower, say at 40fps, we deduct half the difference from its average frame rate and the desired 60fps, giving it a HEXUS.bang4buck score of 30 marks. The minimum allowable frame rate is 20fps but that scores zero.

² the HEXUS.bang4watt score is a crude measurement of how much normalised performance the GPU provides when evaluated against system-wide power-draw that's shown in the table: the former is divided by the latter. We're using the peak power-draw numbers obtained by running real-world Crysis 2.

It's important to remember that our bang4buck is based on a few titles and doesn't take other architectural advantages into account; power-draw, operating temperature and noise output isn't considered. For the purpose of this metric, we're evaluating how much gaming performance per pound each configuration offers.

Summary

The value analysis shows us just where the two Pitcairn cards stack up once aggregate gaming performance is taken into account. The graph is ordered by Bang4buck performance at 1,920x1,080.

Radeon HD 7870

On our six games the Radeon HD 7870's aggregate performance is above the HD 6970's and midway between the GeForce GTX 580 and GTX 570. This correlates well with the commentary on the individual gaming pages. Take the expected £260 retail price into account and the Bang4buck is competitive against other GPUs in its class. The excellent power-draw means its Bang4watt is above average, too.

Radeon HD 7850

Radeon HD 7850's performance, meanwhile, is a smidge better than HD 6950's and about the same as a GeForce GTX 560 Ti 448 once both resolutions are factored in. Throw in some pricing and its Bang4buck is also commendable. Just like the HD 7870, the Bang4watt is very good, as well.

The Value Angle

So what we're really saying here is that AMD has priced the two Pitcairn cards at levels that make them good, but not outstanding, choices. Honestly, a brand-new architecture should provide a significant boost in performance at the same price point as incumbent cards, practically forcing the enthusiast to purchase the new technology. AMD, however, is understandably keen to keep profits up by merely offering an acceptable price that doesn't rock the boat.

We believe that it will take the introduction of NVIDIA's mainstream Kepler GPUs, also hewn from a 28nm process, before AMD is forced to cut the price and profit margins on these HD 78x0 cards. From a business point of view, for now, AMD doesn't need to sell these cards at lower levels: they do the intended job.