Knowing when to retire PCs from GIMPS?

[piforbreakfast]

Almost two years ago I got a good deal on 10 refurbished desktop PCs, not sure the RAM, which I intended to use solely for GIMPS before realizing they would be most useful for double-checks rather than primary exponent crunching. It seems like over the past couple months, about half of those PCs seem to be automatically shutting down every few weeks and I have to reboot each machine. I've not had this issue at all with the three desktop gaming PCs and the one gaming laptop which have been my best workhorses. The desktop gaming PCs have never shut down except during a recent power outage, and the gaming laptop only reboots for automatic updates every couple months or so. So I guess my question is, given the demands of GIMPS on computer hardware and software, how have the rest of you come to the eventual realization that it's time to retire a particular machine? I don't mine the frequent reboots on these double-check machines, I'm just wondering what metrics others have used to determine if these jobs are too much for some of the older or lower-end computers to keep cranking out month after month after month. When is it time to put a PC out to pasture?

[VBCurtis]

It's time to retire a PC when the electricity to run it (plus any added AC expense if you run the old ones during summer) would pay for a new machine. Anything from the Core2 era fits this description; sandy bridge era chips are borderline for GIMPS in power-efficiency terms, same for pre-Ryzen AMD chips.

A modern desktop cpu is likely 3-4x the GIMPS production-per-watt of a 2012 machine. How long would it take for 70% of your old-machine GIMPS power cost to pay for a shiny new desktop?

Your shutdowns are likely signs of dust accumulation in the cases. Pop them open and blow out the dust. If your reboots don't go away, you may have hardware problems (e.g. fading power supply, or bad motherboard component) that could lead to unreliable calculations.

[LaurV]

Originally Posted by VBCurtis

...

+1

[kriesel]

What's their power usage, how many Radeon VII GPUs would that feed, how do the throughputs compare, are the power supplies modular and sound, and are the cases readily reusable? For your future utility rates, and an assumed 3-5 year or longer life, what could some power savings pay for? Compare the status quo to the most energy efficient economical system you could configure and assemble, which is probably a modern CPU with enough new ram to support multiple Radeon VII GPUs. Could the existing system support modern GPUs with or without a motherboard upgrade? (Sufficiently old CPUs won't run recent version GPU drivers.) Are you interested in running big-ram P-1 factoring or other tasks the existing systems are incapable of? Is there any salvage value to components you would not reuse? Do the economic analysis and consider what computation types might be enabled by upgrades or replacements. There's a reference info post about cost per work unit versus hardware from a few years ago. Possibly Colab Pro high end GPUs may outperform personally owned Radeon VIIs.

[Dobri]

Essential maintenance and minor upgrades could prolong the usefulness of old computers for DC tests.
For instance, one could detect high temperatures of the CPU cores with CoreTemp (see https://www.alcpu.com/CoreTemp/) and then apply fresh thermal paste as well as clean/replace the CPU fan to avoid CPU throttling.
Replacing the old hard disk with limited SSD storage might resolve some shutdown/reboot issues and also make the I/O read/write process faster.

[Uncwilly]

Originally Posted by Dobri

Replacing the old hard disk with limited SSD storage might resolve some shutdown/reboot issues and also make the I/O read/write process faster.

Setting the machine to boot from a USB stick or from lan can eliminate the HDD altogether and save those watts. Some folks have used headless machines that boot on lan etc., running 2 motherboards of a single PSU (often outside of a standard case). That could save enough watts to make them ok to run a bit longer.

[kriesel]

Minor tweaks won't resolve orders of magnitude higher power costs per unit of work completed.
https://en.wikipedia.org/wiki/Moore's_law

[paulunderwood]

Originally Posted by Uncwilly

Setting the machine to boot from a USB stick or from lan can eliminate the HDD altogether and save those watts. Some folks have used headless machines that boot on lan etc., running 2 motherboards of a single PSU (often outside of a standard case). That could save enough watts to make them ok to run a bit longer.

Using 2 DIMMS on a dual channel motherboard instead of 4 will save you money -- providing you don't need all the RAM.

[paulunderwood]

Originally Posted by kriesel

Minor tweaks won't resolve orders of magnitude higher power costs per unit of work completed.
https://en.wikipedia.org/wiki/Moore's_law

True. In the winter I run old crap to keep me toasty.

[Mark Rose]

Originally Posted by Uncwilly

Setting the machine to boot from a USB stick or from lan can eliminate the HDD altogether and save those watts. Some folks have used headless machines that boot on lan etc., running 2 motherboards of a single PSU (often outside of a standard case). That could save enough watts to make them ok to run a bit longer.

I've run 4 off a single PSU. The 24 pin atx connector can be split 4 ways. The 4 pin 12 volt connector can be split 2 ways, so I used two. This was with 65 watt i5-6600 CPUs.