AMD Radeon HD 7990 6GB Review

Performance Analysis

The HD 7990 6GB went about proving its position as the fastest graphics card in the world unconvincingly, matching the minimum frame rate of the GTX 690 in Battlefield 3 at 1,920 x 1,080 with 4xAA and running just 1fps faster at 2,560 x 1,600. However, in both tests the HD 7990 6GB held a 4-5 per cent advantage in average frame rate. At 5,760 x 1,080 with 4xAA the HD 7990 6GB is a touch (2fps) faster than the GTX 690 again, with a minimum frame rate of 51fps even in this demanding game. Interestingly though, we found that a pair of HD 7970 3GB GHz Edtions were tangibly quicker than the HD 7990 6GB in both the 2,560 and 5,760 tests; by as much at 12 per cent at 2,560. Considering the similar GPU hardware on tap, we’d expect the two cards in SLI to be a maximum of five per cent faster, but the results consistently exceeded this.


Bioshock Infinite’s a recent addition to our benchmarks (yesterday actually) and the HD 7990 6GB flexes its multiple GPU muscles with a vengeance, bettering the GXT 690’s result by 17fps with a result of 117fps at 1,920 x 1,080 and beating the Nvidia card by 4fps at 2,560 x 1,600. With the GTX 690 hobbled by driver issues at 5,760 x 1,080, this again sees the HD 7990 6GB come out comfortably on top, although the 6GB equipped GTX Titan runs it close on minimum frame rate.

Can it Run Crysis 3? Of course it can, although it’s a close run race with the GTX 690 4GB for top honours. At 1,920 x 1,080 the HD 7990 6GB’s minimum frame rate of 74fps is 2fps quicker than the GTX 690 4GB, but at 2,560 x 1,600 the Nvidia dual-GPU card is 1fps faster with a minimum frame rate of 45fps. At 5,760 however the HD 7990 6GB comes out top with a playable minimum frame rate of 30fps: 10 per cent faster than the GTX 690 4GB, and an impressive feat in what is an extremely demanding game.


Less challenging is The Elder Scrolls V: Skyrim, but we still enjoy the occasional bout of wolf-punching and its huge array of mods has kept it relevant. What’s more, AMD looks to have resolved the multi-GPU driver issues we encountered the last time we tested the game with a pair of HD 7970 3GB GHz Editons, as the HD 7990 6GB managed a minimum frame rate of 96fps at 1,920 and 90fps at 2,560; both a shade behind the GTX 690 4GB. Interestingly, despite a minimum frame rate of 42fps at 5,760 x 1,080 the HD 7990 6GB still couldn’t match the GTX Titan 6GB at this resolution; clearly Skyrim just loves those great big single GPUs.

The Witcher 2 also remains a demanding test (we might even turn on ubersampling one day), but here the GTX 690 4GB reigns supreme. The HD 7990 6GB’s minimum frame rate of 69fps at 1,920 x 1,080 is far behind the GTX 690 4GB’s 96fps at the same resolution and while the gap narrows at 2,560 x 1,600, the GTX 690 4GB hangs onto a 14 per cent minimum frame rate lead (despite posting a lower average frame rate).



Our last performance test is Unigine’s Heaven 3.0 benchmark, and here the 7990 again proved faster than the GTX 690 4GB, with a score of 2171 to the GTX 690’s 2043. Bafflingly though we found that a pair of HD 7970 3GB GHz Edition in CrossFire were substantially faster, producing a result of 2442: a 12 per cent increase. Whether this is purely down to driver version (the HD 7970’s were tested using Catalyst 13.1, the HD 7990 6GB its launch driver based on Catalyst 13.3), PLX chip optimisation or some mystery other factor we’re not sure, but it’s clear that on our test rig at least, a pair of HD 7970s in CrossFire are faster than a single HD 7990 6GB by more than the sum of their clock speeds would suggest.

Of course, dropping a pair of high-end GPUs is going to have ramifications on power consumption and the HD 7990 6GB chows down a whopping 480W of system power under load in Unigine Heaven 3.0. That’s a 21 per cent increase over the GTX 690 4GB in the same test. The trio of 80mm cooling fans does give the HD 7990 6GB an advantage in cooling however; in comparison the GTX 690 boasts just a single such fan. The result is a peak load delta T of 54°C; matching that of the rest of the 7900 series cards. What’s more, the HD 7990 6GB is surprisingly quiet under load; it’s certainly no dual-GPU hairdryer like its predecessor, the HD 6990 4GB, but neither is it whisper quiet.