One of my spare time projects I’m recently into is mining altcoins for fun. As most of these projects start small, in my case a single GPU in a desktop PC. Which ended up with an open rig containing four GPU’s. I tried to build a rig that would run stable and energy efficient as possible.

Hardware

I decided to go with the AMD Radeon 7950 cards, they are claimed to be one of the most efficient cards to mine scrypt coins with a high hash per watt ratio. The components below are selected with running a headless Linux server in mind.

  • Mainboard: ASRock H77 Pro4-M (socket 1155)
  • CPU: Intel Celeron G1620
  • Memory: Kingston 4 GB DDR3-1600
  • GPU: 4x Asus HD7950-DC2T-3GD5-V2
  • Storage: Kingston DataTraveler Ultimate 3.0 Gen2 32GB (USB flash drive)
  • PSU: Corsair AX1200i
  • Additional: 4x powered PCIe Riser Cable Extension 1x to 16x

There were a few issues that a raised after adding the  second GPU. I had to change the BIOS parameter ‘Active Processor Cores’ to 1 because of a soft interrupt issue. I also disabled all audio options in the BIOS and be sure ‘Primary Graphics Adapter’ is set to ‘PCI Express’.

Software

For this system I have created a bootable Linux USB flash drive. Have a look at this post.

I started mining Litecoin, which is based on the Scrypt algorithm. Therefore I used cgminer 3.7.2, the last version which supports GPU and Scrypt mining. Recently I switched to mining BlackCoin on the BlackCoin Pool, were it’s possible to mine using the X11 algorithm. X11 uses close to 50% less energy and produces less heat, so this is really handy as summer is approaching. To use X11 I had to install sph-sgminer 4.1.0 from github.

It took some time to have the cards run with optimal (overclocked and undervolted) settings. Currently the following is active:

"failover-only" : true, "no-pool-disable" : true, "auto-fan" : true, "intensity" : "19,19,19,19", "worksize" : "256,256,256,256", "kernel" : "darkcoin,darkcoin,darkcoin,darkcoin", "lookup-gap" : "2,2,2,2", "gpu-engine" : "0-1060,0-1060,0-1060,0-1060", "gpu-memclock" : "1600,1600,1600,1600", "gpu-vddc" : "1.075,1.075,1.075,1.075", "gpu-fan" : "40-95,40-95,40-95,40-95", "temp-cutoff" : "85,85,85,85", "temp-overheat" : "75,75,75,75", "temp-target" : "55,55,55,55", "expiry" : "120", "gpu-threads" : "1", "gpu-powertune" : "20,20,20,20", "queue" : "1", "scan-time" : "30", "scrypt" : true

Happy mining!