If you own Ethereum mining rigs with RX 470 / 480 / 570 / 580 AMD graphic cards with 4GB memory you might have noticed that your hashrates have been slightly going down. Our RX 470 rig has went down from 27-28 MH/s per card to 25-26 MH/s. This drop will continue if you do nothing about it as the DAG files size is slowly overwhelming your cards capabilities.
Source: 1stminingrig.com
Luckily AMD has been working on this problem and released beta Windows drivers to keep those cards running longer at full speed. They received some heat from Linux users for doing it exclusively for Windows at first - however we think they just wanted to test it on the more popular platform first. All in all the Linux drivers are here - follow the bellow instructions to install them on Ubuntu 16.4.
#Install new ROCm Kernel:
wget -qO - http://repo.radeon.com/rocm/apt/debian/rocm.gpg.key | sudo apt-key add -
sudo sh -c 'echo deb [arch=amd64] http://repo.radeon.com/rocm/apt/debian/ xenial main > /etc/apt/sources.list.d/rocm.list'
sudo apt-get update
sudo apt-get install rocm
#edit grub
sudo nano /etc/default/grub
#2MB fragments for Ellesmere are enabled with a grub option:
GRUB_CMDLINE_LINUX="amdgpu.vm_fragment_size=9"
sudo update-grub
sudo reboot
Source: bitcointalk.org
Our rigs Claymore miner output before the install:
ETH - Total Speed: 103.788 Mh/s, Total Shares: 58, Rejected: 0, Time: 00:54
ETH: GPU0 26.037 Mh/s, GPU1 25.850 Mh/s, GPU2 25.989 Mh/s, GPU3 25.912 Mh/s
After the install:
ETH - Total Speed: 111.828 Mh/s, Total Shares: 3, Rejected: 0, Time: 00:03
ETH: GPU0 28.035 Mh/s, GPU1 27.914 Mh/s, GPU2 27.918 Mh/s, GPU3 27.961 Mh/s
Power consumption remained roughly unchanged. However we did our undervolting via card BIOS modding - we've heard that other methods my fail with the new drivers.