Review: Sapphire AMD ATI Radeon HD 4870 X2 2GB

HEXUS.bang4buck

In a rough-and-ready assessment of the cards' bang per buck, we've aggregated the 1,920x1,200 frame-rates for the four games, normalised them* and taken account of the cards' prices.

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

Consequently, the table and graph below highlight a metric that should only be used as a yardstick for evaluating comparative performance with price factored in. Other architectural benefits are not covered, obviously.

* 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.

** cheapest zero-day pricing.

As an example, should a card score 120fps we treat it as 90fps as only half the frame rate above 60fps is counted for the HEXUS.bang4buck - this is the formula: (120-((120-60)/2)). Similarly, should it score 30fps, we count it as only 15fps: (30+((30-60)/2)).

The reasoning behind such calculation lies with playable frame rates.

Should card A score 110fps in a benchmark and card B 160, then card B would otherwise receive an extra 50 marks in our HEXUS.bang4buck assessment, even though both cards produce perfectly playable frame rates and anything above 60fps is a bonus and not a necessity for most.

Similarly, without our adjustments, the aggregated HEXUS.bang4buck total for two very different cards would be identical if, in a further benchmark, card A scored a smooth 70fps and card B an unplayable 20fps. Both would win marks totally 180, yet the games-playing experience would be vastly different.

A more realistic (and useful) assessment would say that card A is better because it ran smoothly in both games - and that view would be accurately reflected in our adjusted aggregation, where card A would receive 150 marks (85+65) and card B 100 (100+0).

In effect, we're including a desired average frame rate, in this case 60, and penalising lower performance while giving frame rates higher than 60fps only half as much credit as those up to 60fps. If this doesn't make sense or you have issue with it, please hit the HEXUS community.

Here's the HEXUS.bang4buck graph at 1,920x1,200. The graph divides the normalised score by the price.

Our new HEXUS.bang4buck numbers are not comparable to our previous testing 'thanks' to the change in benchmarks and test systems.

So why isn't the Sapphire Radeon HD 4870 X2's HEXUS.bang4buck through the roof? The reasoning lies with the scaling of the card, which only comes into its own when run at 2,560x1,600, when the games begin to become GPU-bound.

Putting it another way, such is the raw, visceral power here, that it makes little sense to consider it if playing at 1,920x1,200, because the subsystem can barely keep feeding it data.