Radeon R9 Nano 

Between both our samples, we see the AMD reference board in the lead consistently with roughly a 1% performance advantage.

The card delivers excellent performance that no other compact card can compete with.

High-end SFF graphics cards remained an oxymoron because a high-end VGA is not just the GPU, but also its cluster of memory chips and VRM, which typically take up enormous PCB real-estate and keep the card outside of SFF proportions.

In idle, the single-fan cooler is quiet, though it could be quieter, and an idle-fan-off feature would be welcome, too, as it could prove useful for dead-quiet media PCs.

In reality, the frequencies depend a lot on the actual game played, and the resolution.

The R9 Nano CrossFire, however, offers incredible 4K Ultra HD frame-rates, which should give you a great deal of future-proofing even as DirectX 12 games hit the scene in the coming months.

The latest installment of Activision's Call of Duty Series is developed by Sledgehammer Games who, as the maker of COD:MW 3, has had experience with the series.

Later in this review, we will analyze what effect the throttling has on in-game clock speeds.

I see the R9 Nano as the optimum choice for 2560x1440p gaming, with most titles being well playable at 4K if you turn off AA and are willing to reduce settings a little bit.

AMD did so by setting the card's power limit to 175 W, and the GPU will adjust clocks accordingly to stay within that power envelope.

With the R9 Nano, the power limit is set so low the card is always throttling, effectively capping the board's power at a certain power draw target in this case 175 watts.

At the "Fiji" GPU unveil, AMD CEO Lisa Su unveiled a prototype dual-GPU graphics card based on a pair of these chips, and it drew power from two 8-pin PCIe power connectors.

Here, it's the only option on the market with nothing in sight from NVIDIA because they don't have HBM memory, which allowed for such a compact design in the first place.

The Radeon R9 Nano is the fruition of AMD's gamble of integrating stacked high-bandwidth memory (HBM) and a 4,096 SP pixel-grinder into a compact multi-chip module that eliminates the need for external memory chips, freeing up large swathes of PCB area.

This, in addition to HBM being more energy-efficient than GDDR5, enabled AMD to design the impossibly compact Radeon R9 Nano that can run anything at 1440p and doesn't shy away from 4K Ultra HD.