So yesterday I unboxeded my reference PowerColor Vega 64.
Initially I was dissapointed with my Ethereum Hashing results, I was getting about 30 MH/s. Not bad but only a 10% improvement over my RX480 at much higher power consumption.
Next I switched to the Blockchain Beta Drivers AMD released recently.
35 MH/s. Ok now we're starting to get somewhere.
After some quick research it appears that people are having great results undervolting the card to decrease the power draw and heat. Sounds like fun. Right away I could see I was getting unstable clock speeds. Seems like I was hitting a thermal limit. So I upped the fan curve. That helped but I was still getting a lot of throttling.
Stock the card runs at 1150mv on the core in it's highest power state. I found I was able to drop the voltage to 1050mv without any resistance. At this point I increased the power limited to +50%.
This really helped with stability of clock speeds, but my temperatures were still high. We're talking 75c at at like 95% rpm on the fan. My ambient room temp is in the 20c-25c range.
At this point I'm mining at about 36 MH/s.
I tried underclocking the core to help with thermals. Interestingly this didn't seem to hurt the hashrate at all. Still very stable at, or just above 36 MH/s. I'm running -10% on the core right now.
The real gains start to come when you start overclocking the HMB2 memory. Stock the memory is 945MHz.
I pushed the memory up to 1040mhz and was seeing hashrates in the 38.5MH/s range. 1060 let me break into 39MH/s.
I'm convinced that with a better cooling solution I could push pasted the 40MH/s limit. Right now thermals are my biggest issue. The fan sounds like a jet taking off. Hopefully someone comes up with a good AIO solution for it soon.
Even with all the tweaking the most I've heard people get is around 38-40 MH/s with a substantial power draw. Given the price of these cards to buy I'm not convinced that it's worthwhile buying Vega cards for mining at this time. Unless the price for the cards drop... a lot. I can buy two RX 580 8GB for about the same price of one Vega 64 and get more hashrate for similar power usage.
Check out this review here for Vega cards versus RX 580s for hashrate and power usage.
http://www.legitreviews.com/amd-radeon-rx-vega-64-vega-56-ethereum-mining-performance_197049
New Blockchain Compute Drivers
Those still running old drivers on AMD RX series cards are leaving a heap of hashrate on the table, get yourselves the new AMD Blockchain drivers and give your cards a free boost in hashrate today!
http://www.legitreviews.com/amds-new-mining-block-chain-optimized-driver-tested_197095
You can grab the blockchain compute drivers here
http://www.legitreviews.com/amds-new-mining-block-chain-optimized-driver-tested_197095