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I just bought a new UPS. Now since I started using it I experienced at least 3 random freeze in Windows 7 and it happens during the first 10 minutes of start-up. Note when I say freeze, I mean I literally can't do anything in Windows, everything is frozen including the mouse cursor.
Is it possible that I bought a broken or underpowered UPS? Can an underpowered UPS make a computer freeze?
BTW, this power calculator says I'm under 300W, but I do have 500W PSU.
Update: FEB 9, 2012
I have replaced my APC UPS with another brand: FSP UPS which is the same brand with my PSU. It's been running with no problem for the last 5 days.
In reference to my answer below: Could it be really true that non-SmartUPS APC models are not compatible with active PFC PSUs? I find it hard to believe since most branded PSUs are active PFC.
If your components draw 300 W from a PSU with 75% efficiency, the PSU will draw 400 W from the UPS. – Dennis – 2012-01-28T17:47:58.550
1A UPS can expose problems in the PC power supply. If it's a cheap, no-name power supply or pushed to its limits, it may not meet the ATX specification's hold up time requirements. This usually causes reboots or shutoffs though, not freezes. – David Schwartz – 2012-01-28T21:54:52.547
@david i'm having exactly that situation on a machine and its been driving me mad. I'm going to try a new psu as what you say makes sense. – Sirex – 2012-02-03T10:39:55.207
So plug the PC back into the wall and bypass the UPS and see if the problem continues. If it does, it's not the UPS. If it goes away, take your UPS back to the shop and exchange it for a more powerful one or if you can't, sell it off on ebay and buy a better UPS. – Matt H – 2012-02-03T10:55:18.257
from what i understand, the problem actually occurs with good psu (that have PFC) and good ups units (i.e: APC). So buying a better one won't actually help. – Sirex – 2012-02-03T11:23:34.883
1@MattH You are certainly correct that if the problem happens without the UPS, it cannot be the UPS's fault. But it is not the case that if it only happens with the UPS it must be the UPS's fault. It can be the power supply's fault. (For example, if it doesn't meet the ATX specification's hold up time requirements, it can fail with a UPS but work fine without one.) – David Schwartz – 2012-02-03T20:00:22.540