Introduction
Crypto mining has become a divisive issue. Miners gobble up popular graphics cards by the armful, depleting inventory and driving up prices. Gamers are left to pay exorbitant prices, sometimes as much as double, even for mainstream GPUs. A little animosity between the two camps is therefore understandable.
But even on the pragmatic side, cryptographic mining never made much sense to me. The profit margin is often so short-lived that by the time the average tech enthusiast hears about it, the bubble is ripe to burst. Once a mining algorithm moves to application specific integrated circuits (ASICs), it's impossible to compete otherwise. Even if the crypto currency du jour doesn't go ASIC, the mining pool can get saturated, and anyone without a quad-GPU farm (or better) may as well be trying to get to the moon with a sliderule (wait, we did that . . .).
But does that mean Ethereum mining is unprofitable for newcomers? Can you start mining at minimal expense? How about with no start-up costs at all?
The Idea
The recent drop in Ethereum's monetary value combined with the vastly increased mining difficulty has severely decreased the profit margin. It's certainly past the point where anyone buying a new, dedicated mining rig will see a good return on investment (ROI). Even if you spent a relatively meager $1200 on a new setup, you'd need to net at least $100 a month for a year to just break even. Ethereum's volatile nature and pending shift to a proof-of-stake model makes it unpredictable. Only the most desperate or foolhardy would buy new mining equipment at this point expecting to make a profit. So let's look for another attack vector.
The key to faster returns is minimizing initial costs. Unless you can get someone to pay you to take GPUs off their hands, the best you can hope for is free. Much as we may wish it, merchants don't give their merchandise away, and not everyone can expect to win raffles and prizes. But old components sitting on a shelf don't cost anything. With a little luck (and apologies to Dire Straits), you can go mining for nothing, bits for free.
Gamers and computer enthusiasts upgrade their systems more than just about anyone. Motherboards, CPUs, and graphics cards sitting around after an upgrade are the perfect starting points for a hobbyist mining machine. You've already paid for these components and extracted value out of them. What's more, you know their history and how well they've been cared for, which isn't necessarily the case when buying discount used parts on eBay. With sufficient leftovers, you should be able to cobble together a competent mining machine, even if it's not terribly impressive.
The GPU is still the biggest factor in determining mining performance and which card you have matters greatly. AMD cards are still king in total mining performance, just as they were in Bitcoin's early days. Nvidia microarchitecture (through Maxwell) wasn't focused on general purpose computing like AMD's Graphics Core Next. Actual hash rates will vary between different mining software, operating systems, and drivers, but even a GTX 980 Ti can't keep up with, say, an older mid-range AMD card. Nvidia has made changes in Pascal that make 10-series cards quite capable miners. Then again, if you're using a recent generation Nvidia card for mining, you're more likely mining on the side with your current machine rather than making a dedicated mining system out of spare parts.
Mining Ethereum at this point requires a 3GB GPU because of the size of the DAG file. DAG stands for Directed Acyclic Graph and is essentially a database of the existing blockchain. In order to mine the next block, your hardware needs to be aware of all the existing blocks. As of this writing, the DAG is just over 2GB, and it only gets bigger with each new step, which happens at least once a week. The vast majority of miners load the entire DAG into VRAM. Without sufficient capacity, the GPU can't even begin mining operations.
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