Why is my PC rebooting at power fluctuations even though its connected to UPS ?

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computer_newbie1

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Jan 20, 2014
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Hi all, Its been 3 months since i am trying to find the issue. why is my PC reboot when the power drops or comes back online or even sometimes at power fluctuations happen Even though i have connected UPS.

240 volts AC location

my machine specs.:
SMPS : Corsair VS450 VS Series™ - 450 Watt Power Supply
CPU : AMD FX(tm)-8350 Eight-Core Processor
Motherboard : Gigabyte Technology Co. Ltd. 970A-DS3P
RAM : 2x Corsair Vengence 8GB DDR3 [currently using only 1 as another is sent to replacement as it was showing errors in memtest]
HDD: 1) Samsung SSD 850 EVO 120GB ATA Device - 120 GB
2) WDC WD20EARX-00PASB0 ATA Device - 2 TB
3) WDC WD5000AADS-00M2B0 ATA Device - 500 GB
GPU : NVIDIA GeForce GT 610 - 2 GB DDR3
Keyboard and Mouse : Dell KM636 Wireless Keyboard and Mouse
Cabinet : DEEPCOOL KENDOMEN TI MID TOWER COMPUTER CASE (BLACK) - 5 fans

OS : Windows 7 x64

here is the export of CPUz cpuz specs

here is power supply calculated https://outervision.com/b/LNvNyO


my machine power supply flow

MAINS LINE => POWER STABILIZER => UPS => PC

my location faces often power outages and low/high voltage and power fluctuations, more on this later

here is my story and what i have tried so far.

from last 3 months my PC started rebooting at the time of power goes and when power comes back online. even though UPS is connected.

so i sent UPS to repair , technician said UPS is fine.

######PC reboots again


I bought voltage stabilizer, and connected it before my UPS.

######PC reboots again

i called UPS company and asked them to visit my location and fix the problem if there is any in my home connection,
Technician came and lowered the output voltage of UPS to 227 from 238 .

######PC reboots again

i again called UPS company. This time the Technician comes and replaces the Motherboard of my UPS with a latest version/model.

######PC reboots again

i checked earthing connections in my home and added additional earthing wire to be on safe side.

######PC reboots again

i suspected the issue is with SMPS.[corsair vs450]
so i started my another old PC which is core2duo to check if this one also reboots.
to my serprise code2duo does not reboots but
FX8350 reboots

###### only FX8350 PC reboots again, and core2duo does not reboots

so i came to conclusion that CORSAIR VS450 is faulty.
So i installed core2duo's SMPS which is also 450watts to my FX8350 machine.

######PC reboots again


now conclusion,
1) eaither SMPS cant handle my machine load, (but it worked for nearly 2 years so why now? )

2) Motherboard is faulty

3) CPU is faulty

4) act of god ?

i really need your help guys.

i dont play games, no overclocking, its just for my regular work and developing work in PHP, C++, JS, etc etc.
I keep PC on 24x7.

to check if UPS is working fine, i randomly switch off mains power supply and PC doesnt reboots as UPS comes online.

so what is causing this issue ? and what needs to be changed ?

 
Solution
BFG-9000
It means I would certainly prefer the 750 over the 650 for the same price, because it's better than the 650 in every way except efficiency at 300w.

UPS units also often seem to fail to meet their stated specs for switchover time, if you consider that the time until the waveform completely stabilizes. 28-30ms is fairly typical but well, you can look at the waveforms for yourself (it seems to depend on where in the AC cycle the outage occurs). Even glitchy power should be better than no power at all, but some PSUs may just be so unusually sensitive to such input they could be considered to be incompatible.

The original IBM XT and AT PCs from 30 years ago were infamous for having PSUs that were so sensitive to...
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The problem may be from the MB, you may try go into the BIOS to disable two or even three cores, then try use the PC again. If the PC runs fine after you disabled the cores, you know the problem is from the MB. But if the PC does the same, something causes the problem.
 
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any specific cores, ? or it does not matter .

are 3 hdd causing it ?

trying to disable 2 cores now , later will try 3 cores

following this
https://www.youtube.com/watch?v=9Dhsr4K4mQk

edit1:

i have found CPU CORE CONTROL in BIOS.

previously it was like this

uMJwTnc.jpg


but there are not much options like which core to disable or not, so i chose bare minimum settings like this.

t7w7Tpc.jpg


now active cpu stats shows like this

3NcDdSh.jpg


i hope, what i did is correct.

thanks
 
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indeed, that is the next test, right now i am testing surge / spike guard .

so current flow is like this.

MAINS LINE => SPIKE GUARD => POWER STABILIZER => UPS => PC

previously it was like

MAINS LINE => POWER STABILIZER => UPS => SPIKE GUARD => PC

PC is up from last 9 hours, will see what happens.

Thanks, will update this thread.
 
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update, apparently my so called SPIKE GUARD was just simple power strip so pc did reboot.,

now i am again testing above same test with proper SPIKE GUARD.

one more thing i noticed., PC reboots only if its on high load, i mean if its working on full load ., mining bitcoins etc

why is that ?

who is not capable of handling such load ? PSU / UPS ?
PSU is 450 watts
UPS is 880 watts
 
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ATX PSUs have a rating called the hold-up time. This is the time the PSU can deliver a full load after the AC power is disconnected, and the very minimum allowed by the ATX spec is 16.7ms. That's 1/60 of a second, so at 60Hz AC you can see it's only 1 AC cycle.

Unless the UPS is a double-conversion type that always runs from the batteries, it's going to take a finite time to switch-over to standby battery power. If this time is longer than the hold-up time, then PSU output will be momentarily lost and you get a reboot.

PSUs don't always meet their claimed spec for hold-up time, especially when they get old and the primary capacitors have lost some of their capacity. But if you aren't drawing the full load from a PSU its hold-up time will understandably be longer. So an oversized PSU may not reboot when a normally sized one will.
 
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What do you know, the cheapest VS series Corsair PSU is only rated 10ms at 80% load so would only last 8.0ms at full load which doesn't even meet half the minimum requirement for ATX PSUs. At least they have carefully documented how trashy they are in their very detailed spec sheet.
3.2.11. Voltage Hold-up Time
The power supply should maintain output regulation per Section 3.2.1 despite a loss of
input power at the low-end nominal range—115 VAC / 47 Hz or 230 VAC / 47 Hz—at
maximum continuous output load as applicable for a minimum of 17 ms.
Click to expand...
 
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WTH , thats very shady technique.

which PSU you suggest ? for full load e.g. mining bitcoins. i am not actually mining bitcoins but just heavy calculations., using 100 cpu.


 
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how much/what wattage ?

as per my UPS specs
Changeover ::

Switchover from Mains to UPS and UPS to Mains : Automatic
UPS Transfer Time ≤ 15 msec.
Click to expand...

imho my UPS is 880 watts so i should get PSU of 750w to be on safe side .
thanks
 
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It's generally safe to go ~30-40% oversized without falling far off the efficiency curve, so ~500-650w should be OK. I know some PSUs in that range don't even turn on their fans below 300w so would be pretty quiet. If you want to go higher than this then I'd suggest reading reviews where they actually test the efficiency curve, because some of them are shockingly poor at low loads.

If your UPS is rated 880VA that definitely doesn't mean it can output 880w, but it doesn't matter as your PC simply cannot draw that much power even with a 1000w PSU installed. Unlike PSUs though, higher is always better for UPSes because batteries are sized so at full load they are generally only rated to run for ~5 minutes, and that's when the batteries are new. The higher VA rating not only means longer runtime at a lower load, it means after the included batteries wear out you can replace them with car batteries and operate it continuously at the lower load without overheating it.

I have a 3000VA UPS that can even run the blower fan on my gas furnace for quite awhile. If an outage looks like it will last a long time, the big UPS allows everything to continue operating normally until I decide to go hook up my manual generator.
 
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its 1100VA UPS gives 880 watts as per specs.,
i am so frustrated at this issue, i don't even mind the fan noise. or any other noise , i just want my machine to run 24x7.

so far i have shortlisted this one

https://seasonic.com/product/prime-650-w-titanium/

they claim to have hold up time of 30ms.

but looks like seasonic does not have service center in my country i.e. India

and i gotta get PSU which has service center in India in case something bad happens to it.

if new PSU is gonna cost that much then i gotta check how much does the online UPS costs., and whichever is cheaper .

on more searching looks like

SSR-750TD and SSR-650TD costs same here.
this is 650TD http://www.ebay.in/geb/ImportHubViewItem?itemid=302021786802

this is 750TD http://www.overclockerszone.com/seasonic-750w-prime-series-modular-power-supply-w-80-titanium-certification/

i really appreciate your input. thanks.

any other suggestions ., are welcome.


Thanks.
 
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Those are some very nice power supplies, and of the two I would choose the 750 for the probably longer hold-up time, because its maximum efficiency is at the 300w range you are using, and as it's quite a bit quieter than the 650 at 400w in case you add a GPU for some hardware acceleration.

While the 650 is a smidge more efficient right at 300w, for the same price the 750 is a no-brainer.

That said, Delta has three PSU factories and 11 sales offices in India, so you are likely to have a much easier time with support from them! Their focus is more on reliability and clean power than noise or efficiency though.
 
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i didnt understand this , sorry for my bad english., so what are you saying ? 650 is better than 750 ?

i have found seasonic service centers in India, and already talked with one., so if i am going to buy PSU, it going to seasonic.

thanks, as now i can easily replicate the issue., i am going try same thing with friends UPS today.,

boot up PC, start high load application/stress test, switch off mains suply and see if UPS kicks quicker to prevent the reboot.

i dont mean to doubt you, but what if i buy the PSU and system still reboots ? i mean what if UPS is takes more than 30ms . to switchover.

is there a way to find UPS switchover time. ? i have already checked the UPS specs and they say <= 15ms.

ill try with small online UPS, in between my current UPS and PC. to take charge for that 30ms i.e. switchover time.,



 
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It means I would certainly prefer the 750 over the 650 for the same price, because it's better than the 650 in every way except efficiency at 300w.

UPS units also often seem to fail to meet their stated specs for switchover time, if you consider that the time until the waveform completely stabilizes. 28-30ms is fairly typical but well, you can look at the waveforms for yourself (it seems to depend on where in the AC cycle the outage occurs). Even glitchy power should be better than no power at all, but some PSUs may just be so unusually sensitive to such input they could be considered to be incompatible.

The original IBM XT and AT PCs from 30 years ago were infamous for having PSUs that were so sensitive to even tiny power glitches that ferroresonant power regulators were quite popular back then, as every business and hospital had to have them to keep their computers from rebooting all the time. That's why the ATX standard of 1995 included a hold-up time spec at all. Perhaps you could find such a surplus conditioner as they may be old but still work--they use a resonant LC Tank circuit to continue generating AC for some cycles after input power is lost. I do warn you that they can generate quite a loud hum, particularly when put under heavy load.

Another option is simply to replace the (usually two) large capacitors in the primary side of the PSU with much larger ones. Doubling their capacitance doubles hold-up time. Going too large though would create such a large inrush current the UPS could shut down when the PSU is switched on. Good luck!
 
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Solution
okie., as i know what is the issue,
i have shortlisted 3 options so far, in ascending order of price.

1) get small online UPS and put it between my current UPS and my PC
2) get seasonic 750w smsps / 850w smps
3) get big online UPS and use it instead of my current UPS.

i have not tried any of the above ways.
ill update this thread, once i try any of them.

thanks
 
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i got "APC BX1100C-IN 1100VA 230V Back UPS"

connected it like this way

MAINS LINE => INVERTER => UPS => PC

######PC reboots again



then i ordered
"Corsair CP-9020098-UK VS Series VS650 650 Watt Power Supply Unit"

and PC DIDNT REBOOT.


looks like my SMPS/PSU was faulty after all.

Thanks everyone who has helped. Thank you for your time.
 
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