Thursday, March 8th 2018

Confessions of a Crypto Miner: CPU Mining

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Welcome back to "Confessions of a Crypto Miner," my column about a crypto miner from 2013 trying to get caught up with the latest standards. I'm presently mining and reporting to you from a dual-GTX 1080 based rig mining zCash.
Today we are going to take a look at mining again - using the CPU in particular. CPU mining is the original form of mining cryptocoins.

Bitcoin and similar programs were originally designed with a miner built into the wallet that mined on your CPU. As time moved on, people realized how ridiculously simple most crypto algorithms of the time were (Bitcoin, as an example, is a simple SHA-256 hash that can be done on something as simple as pen and paper!) They adapted it to execute on GPUs, in parallel, to make best use of these chips' processing power. Some cases (like Bitcoin) are now run almost exclusively on special purpose, many-cored ASIC chips that are built for just this single task. CPU mining became too inefficient for everyone for a long time until some special coins came out based on so-called "CPU-only" algorithms. The most noteworthy of these is probably the Monero coin and its related CryptoNight hash algorithm. It relies on some memory-intensive access principles that CPUs are very good at, resulting in making CPU mining profitable again. The important question now is, "How profitable?" Are CPUs going to be the next thing flying off the shelves, now that GPUs ran out? Let's find out.

My miner, since its inception, has mined zCash, but mining zCash on the CPU is a silly exercise that nets nearly nothing versus electric. As such, I'm turning the CPU to Monero, even though I have expressed reservations about the currency in the past. Those reservations, briefly, are mainly due to its anonymous nature: exchanges have begun to flag this anonymity-centered currency as "high risk," and liquidity on it can be low at times. It's also the posterchild for illegal activity using digital currency, since it can't be tracked, and if any crypto is going to be made illegal via regulation, it's likely Monero. That said, I still don't see why mining on the side with my CPU would be bad - if the numbers suggest a quick and easy profit, so I ran some tests to see what my measly R3 1200 Ryzen can do.
After just a day of mining, a few things became clear. First was that running all four of my Ryzen's cores was not sustainable, as the OS bogged down, and my wallets and miners on the same machine ceased to function. Three cores/threads wasn't sustainable either, as hash rate on the GPU-miner program tanked, and since that's the big moneymaker, we can't have that. So I could only use a measly 2 threads of my 4-core 4-thread Ryzen, and like that it makes just $3.00 per month! That is outrageously poor. I held out hope, though, as power draw only went up by 40 watts, and plugging that into a power calculator shows it costs about well - a little over $3.30.

Yes, mining Monero and selling immediately on a R3 1200 Ryzen appears to be a losing gambit. I can only advise it if you believe that the coin will go up, something I don't believe in.

In order to get data from a more powerful system, I went to my personal R7 1800X based rig, with all of its 8 cores and 16 threads. I quickly found that I can load all eight physical cores before things start to bog down (SMT does nothing for Monero, but it lets the OS chug along with no problems!) What did I get? The short, non-scientific version is, I got roughly six times the hash rate, yielding a more respectable $18.00 per month with no OS slowdown - still rather underwhelming. It also drew a little over three times the power from idle to full load, or about 150W. Granted, my CPU is overclocked, and you could probably improve this efficiency curve, but the bottom line is, no one is getting rich off of CPU mining. It's more a question of whether you should put that idle hardware to work at all, not whether you should buy into it. In my 1800X's case, the 150W power cost is ~$10.00 per month, so I'll turn $8 in profits in the same duration. Is it worth the wear and tear? Honestly, I'd say "yes," but only because I know CPUs can take it. I would never, however, buy a CPU for mining alone. The financials just aren't there. My honest advice for your mining rigs is still to buy the cheapest CPU/platform available, forget about CPU mining, and call it a day. There is no reason at all to splurge on a Ryzen R7 1800X here.

Want to tell me something? Do you think I did something wrong? If so, let me know in the comments below! I welcome questions and feedback of all types and look forward to some great discussion.
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