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So Bitcoin seems all the rage, but it’s way too expensive for us mere mortals. Who can afford a bitcoin, right? But apparently bitcoins are produced by mining them and mining them involves a computer processing mathematical calculations. So I wonder, can I use my Mac to mine bitcoins?

I have one old iMac sitting in a corner that I figure I could leave powered up 24/7 to do nothing else but mine Bitcoins. Is this possible? Will the benefit outweigh the costs?

It’s a 21 inch mid 2010 iMac with a 3.6ghz i5 processor and has 16gb RAM.

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    "Who can afford a bitcoin" - it's possible to buy a fraction of a bitcoin. – legoscia Dec 13 '17 at 11:03
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    Note that you're buying in to a bubble...late in the cycle. – Jared Smith Dec 13 '17 at 13:22
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    Discussed to death over on Bitcoin.SE, see bitcoin.stackexchange.com/questions/41276/… for instance. The answer, for all practical and economic purposes, is NO NO NO NO NO. – Nate Eldredge Dec 13 '17 at 15:10
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    Just for fun back when bitcoin was around $9000 I priced out what a state of the art ASIC mining rig would cost - for about $440, as part of a pool, it was estimated it would net about $800 over the course of one year at which point it would be obsolete. Which is interesting, because the total value of bitcoins it would mine, including electricity, was significantly less than 1, and given that each mined block currently yields 12.5 bitcoins that means that statistically it is unlikely that running 24/7 for a year it would even mine a single block, and would only get $ due to being in a pool – Michael Dec 13 '17 at 16:36
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    A couple of considerations. 1. At times of the year when you're heating your house anyway, the marginal cost of electricity is far lower than at other times; that is, you're using the computer as a heater and burning less oil or gas or whatever. 2. Does a computer use more electricity when it's mining bitcoins than when it's just sitting there powered on but nobody's using it? – John Woolley Dec 13 '17 at 20:04
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Short answer

Is it possible? Yes.

Will the benefit outweigh the costs? No.

Long answer

Without going into a lot of detail, and at the risk of oversimplifying things, in the early days mining bitcoins was easier than it is now. And, as time goes by, it will continue to get harder.

Another contributing factor is that the kinds of calculations needed to mine bitcoins are actually better suited to GPUs instead of CPUs (i.e. a graphics card is better at processing these than a CPU is). So, using your iMac as an example, the best GPU your model shipped with was a Radeon HD 5670 that had 512MB memory and while this may have been okay to mine bitcoins in 2010, it would take so long to do now that the cost of electricity would outweigh the value of any Bitcoin you’d be able to mine (as it now takes a lot longer to mine and the cost of power only goes up).

This brings me to the other factor. There is a real cost in mining bitcoins, starting with the cost of electricity. You’d need to have your Mac working overtime on the calculations 24/7 for literally months to try and obtain a single bitcoin. Trust me, the cost in power will be a lot higher! That is why many bitcoins are now being mined in bitcoin farms in China (i.e. air conditioned buildings with many devices on 24/7).

To my mind, the only way it’d be worth doing on a Mac would be if you were going to have access to one of the new iMac Pros (about to ship in the next couple of days) and it was configured with a Radeon Pro Vega 64 graphics processor with 16GB of HBM2 memory, and you had it running 24/7 at a workplace (i.e. so you’re not paying for the power) and assuming you didn’t have to pay for the iMac Pro itself. But of course that’s not a realistic scenario, and unless your employer was also on board, may risk termination of employment!

Instead, if you want to get into mining, look at a dedicated machine designed for this purpose. Below are some examples:

NOTE: I am not affiliated with any of the products listed above, nor have I any experience with them whatsoever!

As you can see, the above items are not cheap. And, on top of that you need to factor in the cost of running them (i.e. electricity, air conditioning, etc) where you live. So, my advice is forget about using a Mac (or any PC), do your research, and perform the calculations necessary to determine the costs to you and the likely return.

A word on the lottery analogy

As mentioned by various people via the comments below (and those already migrated to chat), many see bitcoin mining as being akin to buying a lottery ticket. While I understand the analogy (i.e. because the odds of success are extremely low, and because someone could mine bitcoins for a whole year with no success while someone else could be successful after only ten minutes), this analogy is actually somewhat misleading.

When someone buys a lottery ticket they essentially end up with a ticket containing random numbers in the hope that those numbers get selected. Now the odds of those numbers getting selected will depend on the lottery you're playing. However, bitcoin miners are not rewarded for essentially doing nothing, because the very act of mining bitcoins is in fact providing a record-keeping service for the overall bitcoin cryptocurrency and payment system. Bitcoin miners (if lucky enough) may get paid (i.e. rewarded) with newly-created bitcoins for this service. Likewise, even the term mining is somewhat misleading. Miners typically produce something, but bitcoin mining doesn't actually produce anything. For more information refer to Bitcoin and Beyond: The Possibilities and Pitfalls of Virtual Currencies.

Nevertheless, using the lottery example is useful to convey that (1) the odds of success are extremely low and, (2) you may get lucky instantly (and therefore the return on investment is excellent) or over the longer-term you'll spend a lot of money for very little gain.

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  • Comments are not for extended discussion; this conversation has been moved to chat. – nohillside Dec 14 '17 at 7:44
  • +1. All true, but you should also mention, for completeness, that mining has an element of luck. Like playing the lottery just once: You could get lucky and mine a block right away, switch off and come out ahead. - Just on average you'll wind up waaay behind. – I'm with Monica Dec 14 '17 at 8:56
  • If you have electric heating (eww) in your house / apartment, you could mine in the winter without much increase in cost: any heat that doesn't come from your computer will come from dumping electrical power into a resistor (aka a heater). But probably a more productive use of spare CPU / GPU time and power is a distributed computing thing like setiathome.berkeley.edu or folding.stanford.edu any of the other scientific endeavours. It won't make cash, but it's a less wasteful way to use power. – Peter Cordes Dec 14 '17 at 11:43

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