Club 3D Radeon HD 7990 6GB review

Performance Analysis

Things got off to a great start for the HD 7990 6GB, with our Battlefield 3 tests demonstrating that it was able to scale excellently over a single HD 7970 3GB, always producing minimum frame rates in excess of 95 per cent more than the single GPU. In each of the three resolutions tested the card outperformed the GTX 690 4GB, topping our charts by 1-3fps every time.

Sadly this positive start didnt continue in Crysis 2, where at 1,920 x 1,080 the HD 7790 6GB produced a minimum frame rate 1fps slower than a stock HD 7970 3GB (albeit with a much higher average frame rate). This result left it just 3fps behind a GTX 690 4GB, indicating that dual GPU scaling is severely restricted by CPU performance at this resolution in Crysis 2. At 2,560 x 1,600, the HD 7990 6GB's minimum frame rate of 52fps represents a 68 per cent performance boost over a HD 7970 3GB, although it still left it trailing the GTX 690 4GB by a fair margin. Its minimum frame rate of 30fps in this at 5,760 x 1,080 meant it was playable and an impressive 87 per cent better than a HD 7970 3GB, but still 7fps behind the GTX 690 4GB.

The updated Catalyst drivers seem to disagree with our Skyrim test, giving the HD 7970 3GB noticeably worse performance than when running the same test with older drivers. This impacts the HD 7990 6GB too, as its minimum frame rate struggled to eclipse that of single-GPU cards at all resoltuions whilst trailing the GTX 690 4GB by a substantial margin.


In The Witcher 2, the HD 7990 6GB scored the exact same result in the 1,920 x 1,080 test as the 2,560 x 1,600 one, even after repeating both tests multiple times, suggesting that AMD's CrossFire drivers are a limiting factor. Its minimum frame rate of 51fps was 25 per cent better than a HD 7970 3GB, but the HD 7990 6GB again scaled much better across three screens, with its minimum frame rate here of 46fps being 84 per cent more than the single GPU and just 1fps behind a GTX 690 4GB.

With the Unigine benchmark being so GPU limited, it's unsurprising to see such good scaling with the dual HD 7970 3GB GPUs. The HD 7990 6GB's score of 3,332 left it on par with the GTX 690 4GB and nearly doubled that of the HD 7970 3GB, which is a great result.

The power consumption of the HD 7990 6GB is massive, higher than any other card we've seen by a large margin when idle and under load. When stressed, the card took our system power draw above 500W, to almost twice the power draw of a single HD 7970 3GB system, and consumed more than 30 per cent extra power compared to the GTX 690 4GB. Though the idle temperature of the card is fairly high, this is forgiveable given that the load temperature is relatively low for a dual GPU card. The triple-slot, triple-fan cooler may be huge, but it certainly does a decent job, and remains audible, but not too loud, when the card is under load.


Our excellent overclock netted the HD 7990 6GB an extra 10fps on the minimum frame rate in Battlefield 3 at 5,760 x 1,080, meaning it was able to consistently pump out almost 60fps across three screens, which is definitely a visual treat, and gives the card a considerable lead over the GTX 690 4GB. Likewise, in Unigine, it leapt even further ahead of the competition, boosting its own score by 16 per cent to 3,876.

Conclusion

Awarding a performance score is difficult given the fickle nature of the card in single screen gaming. Unlike when we first tested the GTX 690 4GB, which offered solid multi-GPU scaling at any resoltuion, the HD 7990 6GB's and its CrossFire driver are clearly more optimised for three screen gaming, where the card consistently enjoys scaling that exceeds 80 per cent. However, it's certainly arguable that if you're dropping £700 on a GPU, it'll be due to your use of Multi-screen resolutions, lessening this blow.

We can't deny the HD 7990 6GB offers respectable value over a GTX 690 4GB for Battlefield 3, as it tops its performance whilst costing £70 less. However, elsewhere the GTX 690 4GB offers much more consistent and improved performance across a range of resolutions, and with much lower power consumption too. The HD 7990 6GB is also disadvantaged by the profligacy of cheap HD 7970 3GBs now on the market, frequently available for just over £300.

It's strange to see a manufacturer producing such a high-end GPU so late in a GPU's life cycle. The HD 7970 3GB first arrived just shy of 12 months ago, yet its taken until now for AMD, or at least, its partners, to produce a dual-GPU version of the card. With its monster power consumption and erratic, driver-dependant performance, it's not a card we'd recommend then, serving instead as an impressive engineering exercise rather than a genuine high-end option. However, kudos is still due to Club3D for finally shipping the card that AMD wouldn't.