Sorry for the wall of text
Not sure how high to put the additional turbo v but I'll try higher now.
The max actual vcore reported by OCCT or CPU-Z you'd want to see is 1.37-1.38v. Realistically you will hit a thermal wall
long before that.
But you do have plenty of voltage 'wiggle room'.
Could it be a faulty psu? I thought this thing had enough power for what I'm doing, I know others have used this same processor with it without issue.
Always a possibility, some of your previous idle fluctuations are interesting.
However, results from software based apps shouldn't be taken as gospel. At best they should be considered a guide, since the only way to get an accurate PSU volt reading is using a tester.
And despite not being able to check load fluctuations - the next best reporting is what's reported in the BIOS.
What is the BIOS reporting your volts as?
Some fluctuation is normal - but if they are fluctuating wildly, which one? (ie 12v, 3v etc)
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Since the 24, 4/8 mobo pin are on the 12v1 Rail, your card should be on the 12v2 rail, which are the Red connectors.
Spec wise, the PSU is fine and is adequate for your card/setup. The 7850 amp recommendation is 24 and peripherals (HDD's etc) use bugger all.
But if it's running 'out of spec' (broken) - that is indeed one possible cause for the sporadic issues you've been having, since a spike or dip can occur at any moment causing a crash.
But it's best to to cover all angles first before having you buy a new PSU 'on the off chance' only to discover a new PSU makes no difference and the problem is something else.
For example it could be a faulty board, the CPU isn't seated 'quite right' (not making full and proper pin/pad contact) or damage like bent pins has occurred to the socket area.
(Of course you are welcome to buy a new PSU if you wish and are willing to take the 'off chance'. I'd personally opt for the Corsair AX650W - but there other good alternatives)
Just some basic double check questions:
Are you using the 8 pin CPU power plug, or the 4 pin plug? And is it firmly secure? Ideally the 8 pin plug should be used.
The same with the 24 pin mobo connector. All locked into place?
How have you got your 7850 connected? - Is it connected using the 6 or 6+2 PCI-E cable connected to one of the the Red plugs?
What you can try next:
It might be time to change tack and actually 'overclock' the system. Eliminate Turbo all together.
But it will be a 'very mild overclock'. 3.6ghz-3.8ghz across all cores, instead of 3.8ghz for just one. It will also be achievable with stock cooling.
It looks like the 1.7 BIOS has been pulled and is no longer available. The latest is now 1.8. - The first step would be to update to that straight away. Normally when a BIOS is pulled and no longer available, a fault has been found.
ASRock > Products > Motherboard > Z77 Extreme4 > Download
(The manual for your board isn't the most informative, so I'm working from mostly 'general' settings. But most of these settings should be found in the OC Tweaker section of your BIOS
►Put the Turbo voltage back to auto.
►BCLK should be left at AUTO or 100.00
►Adjust the multiplier to 38 - this 'should' grey out/disable Turbo. If not, set Intel Turbo Boost Technology to Disabled.
►Leave the LLC at 5, or max settings for now.
► Leave all Power saving settings like Speedstep, EIST etc Enabled.
►CPU Voltage - use a +offset.
ie +0.040 is a good starting place. Check with CPU-Z what the reported voltage is. Depending on temps/crashes etc, you can adjust this up or down. Most likely it may have to go down.
(Just for reference, with my 3770K I use a +0.85 offset with a multi of 47. This gets me a 4.7ghz OC with an actual vcore usage of ~1.28v. Since you are aiming for a
much lower OC - you will not need a vcore this high. Tbh, you shouldn't even need to go above to 1.2v. So if you see the voltage getting this high, lower the offset.
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Offset works by taking your CPU's VID (voltage identification) that is factory set to 'ensure' that individual chip runs at the specified stock clock speed. ie 3.4ghz. Using a positive offset + increasing the multiplier, adds extra voltage to the VID to make the CPU run at the new clock speed ie 3.8ghz. Same idea behind increasing the Turbo voltage.)
All other settings like VTT, PCH, CPU PLL, VCCSSA, Spread Spectrum etc should be left on AUTO.
The fun bit
► Start Testing again. Under load, all your cores should now be 3.8ghz. Keep an eye on your temps. For personal comfort sake, aim for low 90c-mid 90c as your 'max temp limit'.
You may have to fiddle with the offset a bit.
If you start passing OCCT without problems, consider a longer stress test with Prime 95 27.7, or test 'real world usage' like games.
If you
still experince OCCT core failures or game crashes - it might be time to look at either re-seating your CPU (checking for bent pins when you do) or replacing your PSU.
Hopefully this gives you something to work with.