I've been running Linux since 1993. Normally it's a good idea not to claim people are idiots until you know a little more about their experience and technical ability... the 'technophobe' jibe made me laugh... 13 years running a tech company, perhaps you need to realise that bitcoin mining also has a business element - profit is highly dependent on power consumption and only the GPUs matter... I don't want a pissing contest so let's leave the snarks there, eh?
The "you" in the above quote was a collective you, not a personal you. Perhaps I could have been a bit more clear on that front.
BUT... If you're building multiple mining boxes, and are scavenging hardware, then the ONLY real thing that matters is the number of PCIe slots on the logic board, the GPUs you're using, and the quality of your PSU. Hence having ONE system build that works on all is efficient. This is why I recommend the 32-bit platform. Obviously, an old board I picked up for nothing isn't likely to run 64-bit. Otherwise, you need two Ubuntu ISOs and two sets of scripts to build a miner.
It's pretty unlikely that you're going to find a system board that has PCI-e slots that will not run a 64 bit CPU. It's far more likely you'll find a 32 bit only CPU, and in the case of AMD chips, it's unlikely you'll find even that. Intel chips it's a little more likely. 64 bit has been around and been the standard in chips since 2000 or so with the introduction of the Athlon 64. Intel was a couple years behind on that front, but started shipping 64 bit chips in the mid 2000's. If you're scavaging hardware from earlier than that, it's unlikely to have more than one or possibly two PCI-e slots. The number of people that absolutely MUST run a 32 bit install is exceptionally small and catering to the lowest common denominator is counter productive and does a disservice to everyone else.
Also, power concerns are important. Performance of mining is all in the GPUs - processor and system RAM performance is irrelevant. Hence you get *absolutely zero* gain from using 64-bit code anywhere. My thinking is that the doubling of size of all code in 64-bit implementations could increase power consumption of the bits that *don't matter* - the CPU and system RAM. I presume you have a broad knowledge of CPU microarchitecture, specifically how x86-64 operates when switched into 32-bit mode? If running 32-bit code on a 64-bit CPU required emulation or execution in a separate core (as per the old Itanium) then I'd agree completely with you. But at least with x86-64, this is not the case, and 32-bit code can be run using *less of the CPU die* than in full 64-bit mode. Remember that x86-64 has many more registers, for one - the fewer transistors actually *used* corresponds to a reduction in power consumption by the CPU. I'd like to see some hard stats to validate my theory though... perhaps I'll download the 64-bit Ubuntu and do exactly that...
This is an argument that is dragged out and beat to death ad infinitum and has been thoroughly debunked far better than I could do it. Feel free to Google it. The bottom line, though, is that the
theoretical additional power usage from using 64 bit words to transport 32 bit data is so infinitesimally small as to be virtually immeasurable except by very sophisticated equipment. For the purposes of the macro world and more specifically for the extreeeeemly high current draw of these machines when mining, the difference would not even show up in a statistical margin of error on all but the most precise measurements. By all means, if you wish to save a small fraction of a watt per month on your power bill, install the 32 bit version... but you'll use up more power than you save over the life of your equipment downloading either ISO.
Look - don't take this personally - I'm saying that bitcoin mining is the sort of job that could be efficiently done on an Atom Netbook if it had enough PCIe slots! The rest of the system doesn't matter. So why increase the size of the OS, the size of the apps, the amount of data moved around, etc. with 64-bit implementations?
I am not aware of a meaningful size difference between any 64 bit or 32 bit install. If there is in fact a size difference in a given distro, it has everything to do with what's included in the distro and not whether it's 32 bit or 64 bit. But the root of your question is why do it? I've already given you several reasons. Another reason is that what do you do when someone releases a 64 bit miner or other application that you wish to run? You'll have to reinstall... in the meantime, those with a 64 bit installation can run both 32 bit and 64 applications.
I simply stick with the right tool for the job. Unless you're using your miner for something else, there's no need to have anything other than a basic 32-bit build which will work on all boxes you decide to start mining on. Simple as that. I don't consider 'time to move on' or 'keeping up with technology' a valid reason. A mining machine is a dedicated unit where all the work is done on the GPUs. The rest of the system is simply management, control and networking. Can you see my point here?
I see your point and I find it to be somewhat lacking for reasons already stated. If for no other reason than the one I just stated above. You can do everything that you need to do now and in the future on a 64 bit install; the same can't be said for a 32 bit install. There is no downside to installing 64 bit, therefore installing a 32 bit OS is artificially limiting for absolutely no reason.
None of us *want* the CPU, northbridge and integrated peripherals (other than networking...) consuming more power than absolutely necessary. Using a 32-bit implementation reduces the amount of data the OS throws around. I also underclock the CPUs for exactly the same reason. Using a 32-bit build gives a generic 'miner' install that will work on any cheap, old board you throw at it.
Again, you save more power by underclocking your CPU than you will save over the lifetime of your equipment by installing a 32 bit OS in favor of a 64 bit OS... and if the time comes down the road that you decide to repurpose your machine and need a 64 bit, you'll use up much, much more power than you saved just reinstalling the OS.
