Building an Ethereum Mining Rig

A while back I slowly started building out and expanding an Ethereum mining rig.  It was my first, and I had not built a computer in decades.  With the current price of Ethereum, (as of this writing it is at $207.82), I wish I had started sooner and expanded more.

I’ll go over the hardware and the mistakes I made in the process.

The Kit

I started with a kit from GPU Shack.  It came with a motherboard for 5 GPUs, which means 5 PCIe slots, a CPU with Heatsink/Fan, 4GB DDR3 RAM, and a 16GB ethos Media Drive.  I use linux at work so ethos was no obstacle.  I followed the instructions to assemble the parts in the kit.  I missed the step describing how to boot and setup the bios to boot on power up so for months while I had a single power supply (PSU) I also had a PC power button.

I used an old cheap video card to get my initial display as I combed through GPU specs looking at hash rates.  My first GPU I bought new which I recommend you NOT do!  Computer hardware depreciates fast.

The GPUs

I settled on the MSI R9 390.  I liked the potential 30 MH/s the card offered, and they were easy to find on amazon and ebay. This ethereum post mentioned that GPU and I wanted to start mining ASAP. I ignored the power consumption.  I am now questioning that decision.  I have found that these GPUs are robust and I have run them a little hot, but my electric bill will reflect the R9 390’s power consumption.  It runs at about 275 watts.  However, at the current Ethereum prices I am not hurt too badly.  In fact according the Cryptocompare calculator, which is an estimate at best, I am running about 700% + profit margin.  That does not include the initial hardware investment.  I think I paid approximately $200 per GPU and I am now running five GPUs.

The PSUs

I initially bought an EVGA 1300 watt PSU and it worked fine for the first four GPUs.  Once I add a fifth GPU I needed a second PSU.  I used powered risers to connect all the GPUs.  The risers are all connected and powered by the primary PSU.  The secondary PSU is only an 850 watt EVGA.  The intent was to run another three GPUs on it if possible.  I connected the fifth GPU to the secondary PSU and things ran fine for a while.  Then the OS would spontaneously freeze.  When that happens the GPUs keep running but the OS is not responsive to requests or keyboard strokes.  Rebooting the rig fixes the problem, however that is not a solution.

The ethOS documentation hints of this kind of behavior, under the “Limitations of Scope“, “

Dual-PSU systems (if any issue is resolved by using a single PSU, it is a hardware problem).

To fix this I plan to just move that fifth GPU to another motherboard.  We had plans of building a Zcash mining rig, so we ordered another kit.  For now I’ll simply start up another rig on that mobo and fill it up with GPUs as well.

Scaling up

To scale this up I need to find cheaper power.  These currencies are volatile.  In the short term I am looking at putting solar panels on my roof.  We get a lot of sun here in the rockies.  The better solution is to find some kind of cheaper industrial source of power.

Ethereum Casper

With the Casper release of Ethereum, the consensus moves to proof of stake so mining Ethereum will not be an option at that time.  Also, there is a difficulty bomb baked into Ethereum making mining blocks extremely difficult, once it goes off.  Whatever happens, mining Ethereum is not going to be eternal.

When it comes time to switch there will be options to consider.  The mining hardware can be used to mine Zcash, decred, or eth classic.  It could also be used to power golem which will also offer rewards.  I’ll cross that bridge when I get to it.