Will a different CPU accept the existing tasks?
Everything else in the box is the same, I'm just upgrading the CPU.
Existing:
i3-4130 (Gen 4)
New:
i7-4790K (Gen 4)
I've tried to let the WU's run out gracefully but everything arrived from eBay much quicker than anticipated and I've still got about 5 days worth of workunits to process... I don't want to abort any tasks if I can possibly avoid it. Can I keep them while I upgrade the CPU?
Thanks.

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It's probably not recommended, but I don't see why not - provided you're prepared to accept a small risk of things not working out as planned.

I would:
1) Set 'No New Tasks' for all projects.
2) Suspend all tasks, except the ones you're actually running at the moment.
3) Wait until those have finished, and 'update' the project(s) to report those results to the project.
4) Close down BOINC completely - client and manager, not just the manager. Do whatever your operating system requires to prevent BOINC starting when you boot the machine.
5) Install the new hardware. Take good care to ensure that your new i7 is fitted with a good cooling system, and that it is properly in contact with the CPU.
6) Boot the system. Check it thoroughly for error messages, do any software updates that may be advised. Boot it again for luck.
7) Re-enable BOINC, and start it. Run a few tasks - the least important ones first - to check. Ramp up slowly to full production, keeping an eye on the temperatures.

And that's about it. Others may chime in with suggestions - good luck.

I think Richard has covered most of it. If it were an i3 to a faster i3, for example there would be a reasonable chance of even started tasks surviving but I doubt if you would get away with it changing CPU families. - Just putting a faster chip of the same ilk in is something I have done successfully in the past and had running tasks survive.

Thanks Richard.
Only one of my two active projects has workunits at the mo - Einstein. I set both projects to "Won't get new tasks" early yesterday.
It's rotten luck but it just so happens there's a huge 24 hour Einstein WU in progress with 15 hours left! LOL Of course I should have suspended the cached tasks.
I wonder if they'd mind too much if I aborted all 3 running processes? Oh dear :-(
Thanks for the broad coverage of your advice.
And in light of further replies -
In the spirit of curiosity I think I'll put a theory to the test by changing the CPU from an i3 to an i7 without aborting anything and seeing what happens just for the sake of it...
Thanks all. I may be some time - but I hope not! ;-)

PS. Cooling? I'll keep an eye on it...

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If you abort a process all that the project does is send it out to someone else, so no issue for the project.

It's certainly worth trying to see if the change from i3 to i7 is critical for tasks that haven't started.

I wouldn't worry about it. I've changed out the motherboard and the type of cpu from underneath a running BOINC before and BOINC didn't even notice.

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OK. That all seems good!

3 tasks were running on the i3-4130.
And all re-started with the new i7-4790K fitted -

Elapsed~
03:27:00    Gamma-ray pulsar binary search #1 on GPUs 1.22 (FGRPopencl1K-nvidia)
10:14:00    Multi-Directional Gravitational Wave search on O3 (CPU) 1.02 (GW-SSE2)
03:06:00    Gamma-ray pulsar binary search #1 on GPUs 1.22 (FGRPopencl-intel_gpu)

I suppose it remains to be seen if they validate...

A point of note is that the i7-4790K CPU running flat out (but not Turbo), including the IGPU, oscillates over ~10s between 80-90 °C with the old i3 stock heat sink and fan. I guess that'll change on a hot day though. It draws about 77-88 W. The old i3-4130 was steady at around 55 °C and drew around 40 W.

When I'm not gaming or surfing I give the PC over to BOINC at about a 40/60 split during a 24hr period. The i3 , including the iGPU and nVidia GTX 650 turned over about 28,000 (Einstein) a day. We'll see about that... ;-)

It's odd that when I first booted with the i7, leaving both the Turbo and Hyperthreading off in BIOS (careful now), it ran hotter than with Hyperthreading later on. And the i7-4790K seems to use less RAM than the i3-4130 under general use. Weird. But nice. It might be the enormous 8MB L3 cache...

Thanks for the support and encouragement during this potentially terrifying ordeal. Needed it.

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