There is a new Monero (XMR) CryptoNight miner out for AMD Radeon Rx Vega GPUs called Cast XMR that claims to be capable of reaching hashrates of more than 2050 CryptoNight H/s on an single RX Vega 56 or Vega 64 GPU (with a high power consumption). The miner is designed to support CryptoNight/CryptoNote based currencies such as Monereo (XMR), Bytecoin (BCN), DigitalNote (XDN) and Intense (ITNS) to be used with RX Vega GPUs and. There is a 1.5% dev fee included and currently is is available only for Windows OS (binary), no source code due to the developer fee, though apparently a Linux version is also coming soon.
According to the author of the miner is should be capable of providing you with about 1900 H/s at about 200W or over 2000 H/s at 250W of power usage, so if power and cooling is not an issue you might try to get the most out of your RX Vega GPU with this miner. To get the best performance you will need to use the AMD Blochchain Compute Driver (version is 17.30.1029) as well as to toggle the HBCC Memory Segment. While AMD’s new Radeon RX Vega GPUs are a bit buggy as far as mining goes and cause some headaches they are still doing great in terms of CryptoNight mining performance (when they work) and are also interesting option for Ethash dual mining as well, if you manage to keep them cool. Squeezing the best performance out of the RX Vega GPUs requires a lot of power usage and thus a lot of heat being generated, also getting more than 4 of these cards in a single mining rig is still a problem.