Building a Cryptocurrency Mining Rig - Part 1

22 August 2017

tags:+blockchain+diy+hardware

When Ethereum exploded in popularity (and value) in Summer of 2017, Idecided to educate myself about cryptocurrencies and blockchain technology. Aspart of that process, I built an Ethereum (Classic) mining rig.

Here I’ll discuss how I designed and built my miner, focusing primarily on theconstruction of the chassis using OpenBeam, Fusion 360, anda Shapeoko 3. (Later, I’ll discuss BIOS configuration in Part 2,mining strategy optimization in Part 3, and compute performanceoptimization in Part 4.)

If you’re not interested in the design/build process, clickhere to skip to the end result.

Component Research

My strategy for the build was first to choose the mining hardware (the “guts”of the machine), and then design the chassis around it. Having never built aminer before, I began by researching what hardware was typically used formining.

Google quickly turned up Cryptobadger’s blog, which I found tobe enormously instructive. I learned the following from his series on buildinga mining rig:

The power-supply should have headroom beyond GPU consumption.
Few motherboards have sufficient (6+) PCI-E sockets for attaching GPUs.
Few GPUs are optimal for mining in terms of hashes per watt.
GPUs aside, powerful hardware is of little importance.

GPUs

I researched the common mining GPUs, and chose the EVGA GeForce GTX1070 for a few reasons:

They are energy-efficient, and thus inexpensive to power over the long-term.
As low-power GPUs, I assumed they would run cooler than other options. (Thisis important to me because I live in Florida, and didn’t want my miner to bea space-heater.)
These GPUs will be used in Linux workstations when retired from mining, and Iprefer NVIDIA to AMD for that use-case.

Other Components

I also purchased two 3.5-inch hard-drives: an SSD for the operating system andapplications, and an SHDD for blockchains. (I intend to run full Bitcoin andLitecoin nodes, and perhaps others.)

The remaining hardware decisions were relatively unimportant. If you’reinterested in those details, see the bill of materials atthe end of this article.

Chassis Design

With the hardware decisions made, I began designing the chassis.

Research

Once again I started the process by researching what others had done. Thefollowing approach appeared to be relatively common:

Build a lay-flat rectangular frame
Zip-tie GPUs side-by-side inside the frame
Mount the motherboard and power supply beneath the GPUs

Here’s an example from Motherboard:

The lay-flat solution seemed practical and inexpensive, but I had a few issueswith it:

Development

With a strategy in mind, I began to think through the design details. Ieventually decided that:

The power supply should be mounted at the bottom of the chassis to provide alow center-of-gravity and minimize the risk of tipping.
Six total GPUs should be positioned above the power supply, in pairs, inthree 150mm bays. This arrangement would give 3 of 6 GPUs access to cold air,and would sandwich no GPUs.
The motherboard should be mounted off the side of the chassis, on the sideopposite the GPU intake fans (such as not to obstruct cold air intake).

Satisfied with the plan, I began to research construction materials, hoping tofind an attractive material that facilitated rapid prototyping. I eventuallydiscovered OpenBeam, which touted itself as “a low-cost, open-sourceextruded aluminum construction system”:

It fit the bill perfectly.

Building the Chassis

Prototyping

I ordered an OpenBeam set, the “mundane” computer components (motherboard, CPU,RAM, etc.), and a single GPU, and then began prototyping the chassis design.

OpenBeam was ideal for this application. While I have some experience withSketchup and Fusion 360, I personally find it easier to reason through spatialproblems in “meatspace” when possible. OpenBeam spared me from having to modelGPUs and other components in CAD, and enabled me to iterate using real,physical components.

After a few days' worth of experimentation, I settled upon the followingdesign:

(You’ll see a 500W power supply in the photo. I was using it as a placeholderwhile I waited for a 1200W unit to arrive in the mail.)

Testing (Round 1)

With the prototype assembled, I decided to sanity-check the miner’s hashratebefore purchasing the remaining GPUs. I installed Ubuntu 17.04 Server Editionand configured Claymore to dual-mine ETC and DCR, and ran the minerovernight. The hashrates were consistent with what I expected, so I continuedonward.

GPU Installation

With the hardware proven, I purchased and installed the remaining five GPUs:

(These pictures were taken before the final two GPUs arrived in the mail.)

Initially, nvidia-smi could not detect two of the new GPUs, and I suspectedthat the PCI-E risers were defective. After experimentation, however, Idetermined that the risers themselves were fine, but that the USB cables theyshipped with were faulty.

I resolved the problem by replacing all of the PCI-E riser cables with new onesfrom Amazon, having lost confidence in the factory cables.

I also had to update my motherboard’s BIOS in order to detect more than fourGPUs. I’ll discuss that process in detail in Part 2.

Testing (Round 2)

After installing the GPUs, I ran the miner for a few days as a test, and onceagain achieved the (now higher) hashrates I expected. I only encountered twominor problems:

Cable tension would sometimes pull the GPUs together. (You can see thishappening in the photos above.)
Some GPUs were getting hot (~80C).

The first problem was easily solved. I purchased aluminum screws and stand-offsfrom McMaster Carr and constructed locking-lugs to hold the GPUs inplace:

(This would have looked nicer had I purchased shorter screws or tallerstand-offs. Oh well.)

The overheating problem required more thought. The obvious solution was toinstall fans on the chassis, but I was unsure how best to mount them.

As a short-term kludge, I zip-tied a 140mm fan in front of each GPU bay. Thiscooled the GPUs sufficiently for me to begin mining full-time, and freed me tosolve the remaining problems at my leisure.

Side note: I was surprised by how much more effective it was to “suck” hot airaway from the GPUs than to “blow” cold air over them (~7C). I oriented the fansto “suck” air accordingly.

Mounting the Power Switch and Hard-Drives

While I mulled over how to permanently mount the fans, I decided to first solvean easier problem: mounting the power switch and hard-drives.

Wanting to make the job easier, I started by purchasing a double mountingbracket for the hard-drives:

I then designed a panel for the top of the chassis, and cut it from 1/4" Lexan:

I attached the power switch and hard-drive mounting bracket to the panel, andthen attached the panel to the chassis. It held everything neatly in place:

The mar in the photo occurred because my mill failed to withdraw to its“retract height” when travelling to make its first cut. I’m not sure why it didthat, but I suspect that I overlooked some parameter in Fusion 360 that Ishould have set. (I’m really enjoying Fusion 360 so far, but I’ve found that ithas a steep learning-curve.)

Milling blemish aside, I thought the panel turned out really well.

Mounting the Fans

With the drives mounted, I turned my attention back to the fans.

I wanted to position a fan in front of each GPU bay. Each bay was 150mm wide,and each fan was 140mm wide (with mounting holes slightly closer together thanthat).

Because I was happy with the Lexan mounting panel for the hard-drives and powerswitch, my first instinct was to take a similar approach with the fans. Idesigned and cut a prototype mounting panel:

The panel milled perfectly. After experimenting with positioning it, though, Iobserved some problems:

The holes that mounted the fan to the panel and the holes that mounted thepanel to the chassis were so close together (out of necessity) that theirscrews competed for space.
Each GPU bay had somewhat different geometry due to the hardware used tomount the motherboard to the side of the chassis. Accommodating this wouldrequire me to either mill a distinct panel for each bay, or to “jump” someof the mounting hardware with stand-offs.

After staring at the chassis for a bit, I decided to ditch the Lexan panel andopt for a simpler solution - mount the fans directly to a chassis rail:

(The fans are white, though they look somewhat blue in the photos.)

(The blue device sitting on top of the chassis is a fan controller. It hadn’tbeen mounted at this point.)

This approach positioned the fans slightly (5mm) off-center, which is why Iavoided it initially. Functionally, though, that was inconsequential, and Ifound that the aesthetics didn’t bother me. So, I declared that solution “goodenough” and moved on.

Mounting the Fan Controller

The final piece of hardware to mount was the fan controller:

I had initially hoped to mount it above the topmost GPU fan, but the enclosure wastoo deep, and collided with the power switch.

I then changed plans and decided to mount it off the side of the chassis, abovethe motherboard. There existed no convenient way to mount the fan controllerenclosure to the chassis, though, so I disassembled the fan controller to seeif I could drill two holes in its enclosure to use as mount points:

The enclosure turned out to be mostly empty. The useful part of the fancontroller was a circuit board attached to the front panel, which liftedeffortlessly out of the enclosure:

Having discovered this, I discarded the enclosure and returned to my originalplan of mounting the fan controller above the topmost GPU fan. I only had tomake one modification to the chassis: the fan controller collided with ahorizontal strut that connected the tops of the front chassis rails.

The offending strut was structurally unimportant, so I simply removed it.(Thanks to OpenBeam, it only took a few seconds to make this change.)

Next, I once again used Fusion 360 and my Shapeoko to design and cut a Lexanmounting panel for the fan controller:

The fan controller snapped cleanly into the mounting panel, and I reinforcedits fit with Superglue. (In hindsight, I should have been tidier with theglue.) I then mounted the panel to the chassis:

With the fan controller installed, I powered on the machine and tested the fanacoustics. Dependent on the fan controller settings, the fan noise ranged from“barely audible” to “oscillating desk fan”. Even at the highest setting, thefan noise never became unpleasant.

The End Result

Completed photos, daytime and nighttime:

With that, physical construction of the chassis was complete. In Part2, I’ll discuss the BIOS changes that were necessary to bring all sixGPUs online and fix corrupted video output.

If you have any questions or comments, tweet to me at @chrisallenlane.

Proceed to Part 2 »

Appendix: Bill of Materials

I used the following items for the build. (Disclosure: these are affiliatelinks.)

OpenBeam Precut Construction Kit (x1)
OpenBeam 1515 x 150mm, 8 Pack (x1)
Corsair HX1200i 1200 watt power supply (x1)
16 mm chassis switch (x1)
MSI Pro Solution Intel Z710A ATX motherboard (x1)
Intel Celeron G3900 2.8GHz processor (x1)
Kingston 4GB RAM (x1)
EVGA GeForce GTX 1070 SC (x6)
PCI-E powered riser (x1 pack of 6)
USB 3.0 cable (x6)
Seagate FireCuda 2TB SSHD (x1)
Samsung 120GB SSD (x1)
Corsair Dual SSD mounting bracket (x1)
Male to female SATA power splitter (x1)
Corsair 140mm fan (x3)
Fan controller (x1)
Lexan Sheet (x2)
Velcro One Wrap Thin Ties (x1 roll)
Kill-A-Watt (x1)

Appendix: node-nvidia-smi

While experimenting with implementing node wrappers around various miningprocesses, I developed and published node-nvidia-smi, which exposesinformation from nvidia-smi to a node environment.

Building a Cryptocurrency Mining Rig - Part 1 | chris-allen-lane.com (2024)