For GPU thermals we use the Unigine Heaven Benchmark 4.0. This powerful tool is a GPU-intensive benchmark that hammers graphics cards to their very limits and can not only be effectively used to determine the stability of a GPU under extremely stressful conditions, but also check the systems cooling potential under maximum heat output.
Given the size restrictions imposed by the Lian Li PC-Q21A, we are somewhat limited by the choice of GPU. With a maximum GPU length of 170mm, we found the perfect match to be the AMD R9 NANO. Not just because at 154mm (165 inc power lead) it’s diminutive as its name implies, but because this capable little card GPU clock frequencies can jump around a little. To combat this the NANO is given a Power Limit increase of +50 which stabilizes the core speed at 1000MHz, but thermal throttling will still occur if the card temperature reaches 85C+. The PC-Q21A does in fact do a pretty good job of cooling the NANO with a Delta of 52C (76C Max). This can be attributed to the NANO being very close to the case floor, but also because there is nothing really to impede the flow of cool air to the NANO.