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Jul 23, 2017
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How to Build an Energy-Efficient Ethereum Mining Rig

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By Kannon Yamada 

Energy-efficient cryptocurrency mining saves you money, saves the planet, and can make you money. The trick is to maximize your hash rate per watt or reduce your system’s overall energy footprint. Here are the components and configuration settings needed to maximize your computer’s energy efficiency for mining the cryptocurrency Ethereum.

Ethereum Mining Precursor

There are two approaches to reducing power costs when mining Ethereum (or any cryptocurrency):

  1. You can reduce the total wattage consumption of the system.
  2. You can maximize the amount of cryptocurrency mined relative to its power consumption.

Both design styles end up looking very similar to one another. That’s because cryptocurrency mining focuses on two parts: the graphics card and the power supply. The rest of the computer can be little more than scrap heap pulls.

Let us begin with the most important component: the Graphics Processing Unit (GPU).

Parts for Building Your Ultra-Efficient Miner

Energy-Efficient GPUs

The most energy efficient GPUs around come from Nvidia. Unfortunately, Nvidia GPUs aren’t quite as good at solving cryptographic hashes as AMD hardware. More or less, if you want energy efficiency (without paying a fortune for a 1070 or 1080), your only option is an AMD graphics card. The most energy efficient of these is the AMD Radeon RX 460 or RX 470 (or the pricier RX 560 and RX 570). The RX 470 pulls around 145 watts, with the recommended power supply for it producing around 350 total watts. The RX 460 on the other hand, uses a total of 75 watts. That makes it easier to deploy on single-card mining rigs.

AMD Radeon RX 460

The hash rate of the RX 460 is reported to be around 11 mega-hashes per second (MHS). With a “peak” wattage consumption of 75 watts, that translates to 0.147 MHS/W. The 470 produces a hash rate of around 25 MHS with a power consumption of around 120 wattsfor 0.208 MHS/W. Of the two, the 470 offers better efficiency per watt. But the 460 is easier to deploy on low-cost, low-end systems. And the 470 costs a great deal more on secondary markets. More or less, the 470 is running for well over $350 on eBay, whereas you can still get a 460 for around $100.

Note: The more RAM, the better the hash rate of the card. If you can get more RAM, do it.

The RX 460 Is Easier to Power

GPUs like the RX 470 require additional power from either a 6-pinor an 8-pin connector, supplied by your power supply unit (PSU).

Unlike the 470, the 460 draws so little power that it can operate entirely off the power supplied by the motherboard’s PCIe connector (which maxes out at around 75 watts). That means you don’t need an eight or 6-pin connector, so it can almost certainly operate off the energy supplied by what’s known as a picoPSU: a tiny, fanless, highly-efficient PSU.

Energy-Efficient Power Supply

The power supply determines how efficiently a computer pulls current from the wall socket. Unfortunately, the standard PSU converts from wall current (Alternating Current, also known as AC) to Direct Current (DC) at around 70 percent efficiency. That means 30 percent of the power pulled from the wall gets turned into waste heat. Fortunately, a variety of PSUs can convert at 80 percent and higher. When certified by the 80+ organization (TK), these power supply units receive a rating, which varies depending on the load of the unit. The ratings vary between 80+, 80+ Bronze, 80+ Silver, 80+ Gold, 80+ Platinum, and 80+ Titanium. At the highest end of the spectrum, PSUs produce above 90 percent efficiency at all loads, but they tend to cost a fortune.

I prefer using what’s called a picoPSU. A picoPSU generally supplies power somewhere under 200 watts. It also tends to offer higher efficiencies than standard power supplies, at around 80 to 90 percent efficiency. If you’re using an RX 460, you can get away with a picoPSU. The model I recommend is the 160-XT (UK). The XT includes a 4-pin CPU connector.

Mini-Box picoPSU-160-XT High Power 24 Pin Mini-ITX Power SupplyMini-Box picoPSU-160-XT High Power 24 Pin Mini-ITX Power Supply160 watts 12V DC output BUY NOW AT AMAZON$49.99On the downside, you can’t just slap a picoPSU into a case without making modifications. For example, I had to run the DC power jack through my case’s three-pronged female port. On top of that, picoPSUs usually only support a single SATA-powered device. If your case places its storage drives in odd places, you might also need an extension cable.

PSU Case Modification

The Motherboard and Processor

There is only one requirement for the motherboard: it needs to support a full-size GPU. The processor doesn’t matter.

I would normally recommend using an Intel Atom motherboard. Unfortunately, no consumer-class Atom board offers full-sized PCIe x16ports. Also, there’s some confusion regarding how much power the PCIe slot produces. According to its specifications, a PCIe x16 slot can deliver around 100 watts. That should be enough to handle the 100-watt draw of the 460, but some manufacturers include an optional 6-pin connector on cards — just to be on the safe side.

Mini ITX Motherboard

Fortunately, a handful of AMD motherboards include full PCIe slots and low-power processors. AMD released two different lines of processor that offered a winning combination of low power consumption, low cost, and a full PCIe slot: the AM1 platform and a series of motherboards with soldered-on processors. Of these, I prefer the ECS KBN-I/2100 — but these tend to be hard to find and overpriced. Fortunately, the AM1 platform provides similar low build cost and low power consumption. For example, you can find an AM1 dual-core Sempron processor for around $35. And the motherboard costs around $25/£24.70 with Prime shipping.

Motherboard PCIe x16 slot

The Rest of the Computer

The rest of the computer doesn’t matter much. In general, you want a case that can adequately cool either an RX 460 or RX 470 — but GPUs include their own cooling mechanism. The basic idea behind a case is that it shouldn’t impede the GPU’s ability to cool itself. Some people even choose to do open air builds. An extreme few daisy chain together multiple 470 GPUs on Ikea storage shelves!

Sample Build: Super Low-Energy Ethereum Miner

Here’s what my ideal build looks like:

  1. Motherboard + CPU: ECS KBN-I/2100 ($60 via eBay)
  2. GPU: XFX 4 GB RX 460 ($140/£120via Amazon)
  3. Case: RAIDMAX Elements ($30 via Newegg)
  4. PSU: 160XT picoPSU rated for 180 watts with adapter ($80 via Amazon)
  5. RAM: Crucial DDR3 1 x 2 GB DIMM ($12 via Amazon)
  6. SSD: DREVO X1 Series 60 GB SSD ($43/£30.49 via Amazon)

Total wattage consumption: 100-120 watts
Estimated hash rate: 11 MHS/S
Hashes per watt: 11 MHS/100 W = 0.10 MHS/W

A slightly more expensive miner would differ in its PSU and GPU, but otherwise should look identical. Instead of using an RX 460, it might use an RX 470 (or even 480). Unfortunately, the prices of higher end cards has gone through the roof. I wouldn’t advise anything beefier than a 460 — just enough to get your feet wet mining crypto without costing a fortune in build costs and power.

Mini ITX Case

The SSD will ensure that this system is fast to boot and configure, and you could double the RAM by purchasing two 2 GB DIMMs instead of one. This would slightly increase the hash rate for very little additional cost.

Configuring Your Miner: Undervolting Your GPU

Like with CPUs, you can reduce the voltage supplied to the GPU and decrease the power consumed and waste heat produced. Whether or not there’s a trade-off depends on the silicon lottery. Most discrete graphics cards can undervolt slightly without losing anything. However, a small number become unstable, even with a slight undervolt. You won’t know until you try.

If you have an AMD card, it works like this: install Radeon Settings. Run it, and then go to the Gaming Tab:

AMD Motherboard

Choose Global Settings:

AMD Motherboard

Choose the Wattman tab and scroll down until you reach the entry for Voltage Control (mV). From within this menu, you can reduce the voltage. However, keep in mind that your GPU draws a different voltage at each frequency. Personally, I use a 100 mV undervolt at each frequency. So, for STATE 1 through 7, I reduce the voltage by 100. The lowest it can go for the RX 480 is 800, so you’ll notice that the first two entries are at 800:

Mini ITX Case

If this makes your system unstable, Radeon Settings will automatically reset to the default voltage. There is virtually no risk of permanent instability. In the worst case scenario, you can simply remove your graphics card.

Should You Build an Energy-Efficient Ethereum Miner?

I’d say only as an experiment. The technology behind Ethereum, a big leap over Bitcoin’s underlying technology, may one day prove to be valuable. But cryptocurrency is so ridiculously speculative, it’s only worth taking a moderate risk on. I wouldn’t invest thousands into mining unless you really have thousands to spare, and make sure you’re aware of the risks before spending any money.

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