3DMark
3DMark is the latest version of this hugely-popular synthetic benchmark. Making use of DX11 features such as tessellation, compute shaders and multi-threading, it provides modern-day results and is available as a free download.
The first question you're probably wondering is how can a 4GB card beat out the reference 8GB card in the trio of tests, particularly given that it is running slower memory?
The answer has to do with the sustained core speed. AMD's reference card's cooler doesn't enable the RX 480 to maintain the 1,266MHz boost speed at all times. In fact, it drops down to around 1,150MHz routinely. The Sapphire 4GB card, meanwhile, remains at 1,306MHz at all times, while the 8GB Nitro sits very close to 1,342MHz during our benchmarks.