The Components You Need To Build A Low-Cost Ethereum Mining Rig
Nothing was purchased for this article. Everything comes from either my old test benches or my personal stock. As such, calling this "part selection" isn't terribly accurate. Admittedly my old parts might be slightly higher quality and faster than the spare parts of the average computer enthusiast. However, this miner is not stored away at the Tom's Hardware offices. It's running in my own home. Using power I pay for. Dumping heat into rooms I sleep in. Making noise I have to listen to. In other words, it's not a purely hypothetical thought experiment. I can report on what it's like to actually live with one of these systems.
GPUs – PowerColor 290X
I have two R9 290X GPUs from past Z97 and X99 test beds. This may seem like something of a cheat, but it's perfectly plausible that someone would have upgraded a CrossFire 290X setup to a 1070 or 1080 last year. The fact that one of them is liquid cooled is also not far-fetched. I'm simply building a rig with what I have on my shelf. I'll discus overall performance and profitability later. For simplicity, I'll refer to the liquid-cooled 290X as GPU 1 and the air-cooled model as GPU 2.
CPU – Intel Pentium G3258
Mining CPU overhead is quite low, so a weaker CPU is perfectly adequate. For miners buying new rigs, the cheaper CPUs not only save on initial costs, they also save on power draw, thus lowering the power bill. In my case, I have the G3258 I used in my H81 and B85 motherboard reviews. It's actually a little more powerful than is strictly necessary.
Motherboard – Asus Maximus VII Gene
This board is, at once, both overkill and a poor performer for a miner. As a microATX board, it lacks the extra card slots most miners want. It's also far more expensive and performance oriented than any miner would want. However, since I'm not using any PCIe riser cables, it's just fine for my two GPUs. The single spacing for double-slot cards would normally be a problem for adequately cooling the dual 290X graphics card setup. However since GPU 1 is liquid cooled, it has no problem being squished behind GPU 2. The air-cooled card will be on the bottom in an open case, giving it plenty of breathing room. The only other motherboards I have on hand are X99 and the Z68 in my personal machine, so this one is the best choice.
RAM – Patriot Viper DDR3 16GB
This is one of the leftover kits from the Z97 motherboard reviews. It's far more RAM than needed, but again, I'm using parts already on hand. If you wanted to be really strict on power consumption, you could use a single module. For this guide and the mining software we used, you'll need 4GB of RAM bare minimum. If you want to mine long term, 8GB is recommended.
"Hard Drive" – Adata 32GB USB 3.0 Drive
Strangely enough--or perhaps not--spare hard drives are one of the few things I don't have in abundance. The old system drive on one computer tends to get converted to a storage drive when I upgrade. I do have an abundance of portable flash drives, however. I have plenty of SD cards, but all my reader adapters are USB 2.0 only. Clearing off a rarely used USB 3.0 drive gives me a little extra read and write speed and also some extra space to experiment. Still, even a 16GB drive is more than big enough for the end product.
Power Supply – Antec HCP 1200W
Here's the sticky bit. While you may upgrade your motherboard, CPU, GPU, and storage, quality power supplies are something we all tend to carry over between builds. Even if you do have a good PSU available, it's unlikely to be capable of running multiple GPUs at full tilt. The 1200W model here comes from the X99 test bed. While it's just under half load with this particular system, even hobbyist miners can easily pull 600W – 800W from the wall. Of all the parts used in my "free" miner, this is the most unrealistic.
Case – HAF xB Evo
Mining systems consume lots of power and put off just as much heat. Most are not in an enclosure of any kind, but are instead on open beds or even custom made frames. I didn't want to buy anything new, and didn't feel like exercising my carpentry and fabrication skills. I run my xB Evo case without any panels on it, so airflow isn't an issue. It also makes things easy since the X99 cooling loop, which includes GPU 1, is already mounted to the case.
Cooling – Custom liquid loop and various fans
As previously mentioned, I'm using the same case and liquid loop used for X99 reviews. This is for convenience and speed, not because it's necessary for the whole build. GPU 1 came with a water block direct from the manufacturer; I don't have an air cooler to mount on it. I'm also using an mATX motherboard, which wouldn't accommodate two regular 290X cards because the coolers on them tend to be 2.5 slots thick.
Because I already have to use liquid cooling, I decided to save the time and not break the loop apart. This means the lowly 53W TDP Pentium is being cooled with an EKWB Supremacy Evo water block and two radiators (one dual 140mm, one triple 120mm, both 40mm thick). Ridiculous, I know. Had I a larger motherboard for better GPU spacing and two air-cooled GPUs, I could have easily gotten away with a stock Intel heatsink alone for the CPU.
OS – Lubuntu 16.04 LTS
Extra hardware may be common on parts shelves, but it's not fair to expect anyone to have an extra copy of Windows on hand. Since I'm going for a "free" mining rig, using a truly free operating system seemed like the way to go. Linux can also be installed and run from a removable USB drive, something Windows 10 doesn't allow. The flavor I went with is Lubuntu. It's a stripped-down version of the Ubuntu distribution, meant to be extremely lightweight for use on older computers and netbooks with low processing power. As such it's extremely small, needing less than 8GB of space for a full installation. Running the machine off a USB drive means slower performance for generic system tasks and responsiveness, but it has zero impact on crypto mining.
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