I thought this was the best of several possible places to put this. Moderators, if you disagree, shift it.

People have said that it's not economical to have a pc mine Bitcoin or other virtual currency due to power consumption; With this year's Halving, that would particularly be true for Bitcoin.

PC Economics: Typically 8 core cpu, 2×gpu etc needs a 650-800W PSU, fans, etc which with power supply (in)efficiency would consume over 1KW = 1 unit per hour. Capital outlay would be over €1000 (= $1100). That's uneconomic, so we're told.

I now propose a different scenario. Is this economic? The RazPi 4 has an A-72 Cortex 4 core running @1.5Ghz with a decent FPU & GPU allowing Hard Float compilation (= always use the FPU for Maths operations). Options include 4G, and now 8G Ram. A Flirc case is available with thermal conductivity from chips to case, eliminating the need for a fan.

Power Consumption is 5V3A = 15W with power supply (in)efficiency=20-30W, & capital outlay = €100 - €120. That's at least 8 of these units for the capital outlay of your pc, and 30 of them(!) for the running cost of one pc.

First, I freely admit that am quite clueless about hardware. But I have a hard time believing that 30 of those little things could challenge the raw power of an 8 core 2x gpu machine. If they were even close to that powerful wouldn't we see more desktops and servers based on arm > i386 / amd64? If the power is there then the entire industry has failed in that regard, and I really doubt that.

That thought struck me too. That's why I asked.

This idea might be a runner, it might not. If you look at running costs only, it's a much poorer spec'ed 120core cpu with 30 x gpu. Even reducing that number to one third to adjust for frequency & efficiency, it's a 40 core cpu, with 10x gpu. The gpu isn't anything to write home about, although it claims 2 screens @4k hdmi @60Hz. It takes someone with more knowledge than me to say an 8 core, 2×gpu box is going to whup a 30 core, 10×gpu box on efficiency alone.

What you're suggesting there is shifting from a large general-purpose computer to a small general-purpose computer.

Even amateur miners stopped using general-purpose computers years ago, and switched to using specialized chips that are designed to do nothing else but the calculations required to mine bitcoin.

https://en.bitcoin.it/wiki/Mining

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30 x 25 Watt = 750 Watt. I doubt an 8 core machine with 2x GPU will consume THAT much power.

Sorry, my analysis was the Engineering 'worst-case' of 30² = 900W. You are quite correct, it's not that bad. Fully 1 Amp is dedicated to 2×usb-3.0 ports, so ignoring them drops power to 10W, making 20W a more reasonable worst case.

Well, I suppose I was thinking gamer class CPU, with 2 nvidia GPUs = 3 heatsink-melting cores being cooled be big fans. Inefficiency results in a power supply because some necessary lines (e.g. -5V) which are still supplied use no current whereas 5V & 3.3V use huge current, but all come from the same transformer. The Low voltages in particular are awkward as it supplies a variable and tightly controlled core voltage. There's hardware design challenges there, for which you usually pay a price in efficiency.

So let's say a 650W of power. At 70% efficiency (=good) = 928.57W; at 65% (more likely) = 1000W from the utility

ASIC is actually the way to go, most probably. I frankly didn't know they were there. FPGAs are general purpose devices configured to your VHDL and typically get you into the hundreds of Mhz. Application Specific Integrated Circuits involve a known good design manufactured by a specific company using a mask which you pay for. It's not for small volume, but that takes you into the Ghz, depending on your fab size.

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SUV's are bad enough, bitcoin mining, no thanks.

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You're a spammer; reported.

I know it's an old thread revived by a spammer, but I have recently done some "anecdotal research" into this.
I wanted to know how much electricity my machines actually consume.
I borrowed a professional grade watt meter and started measuring.
I then compared the measurements to the recommendations made by online PSU calculators.
Without going into too much detail, the actual consumption comes nowhere near these sites recommend.
Equipped with a fairly normal 400W PSU, I couldn't get my desktop PC to consume more than 67W. That's full stress on i/o, CPU, memory. Fan screeching.
Full usage (browsing, video, music etc.) is about half that.
That's with 1 SSD and 2 HDs, a cheap intel quad-core CPU and no dedicated graphics card.

I repeated the measurements with 2 more PC-compatibles and the results where equal.

I often see people compare desktop computers' consumption to ARM SOCs' consumption, using the label of the PSU as a base - that's completely wrong.
ARM SOCs use less electricity, yes, but not by orders of magnitude.
[ And if you want to connect a spinning hard drive to your raspi, it will consume significantly more. ]