I found this thread on LinusTechTips forum:
The EVGA G2 lineup is considered by many to be very high quality, the P2 considered fantastic, but the latest testing by professional reviewers shows that some or perhaps all of these units have a serious flaw that won't harm the PSU but could harm your other hardware. It's important to explain the concepts before anything. Very few reviewers test for this stuff - Aris, who does power supply reviews on Tomshardware and Techpowerup, very recently started a new test. This new test shows that many units have newly revealed flaws, and this problem exists with the EVGA G2 and P2 lineup. The EVGA G2 series is a direct copy of the Superflower Leadex Gold series. The EVGA P2 series is a direct copy of the Superflower Leadex Platinum series.
Old Hold-Up Time Tests
In the past, most power supply reviewers would test "hold-up time" as the amount of time from when there is AC loss (i.e. power outage) to when the unit shuts off, while under full load. For example, if a power supply is under 100% load and there is a power outage, if it takes 20ms for the power supply to shut off, it would be defined as having a hold-up time of 20ms. However, this is not an actual test with what hold-up time really is, and new tests reveal new realities. The old hold-up time tests are not in exact accordance with the definition of hold-up time.
Hold-Up Time
Hold-up time is defined as the time period from when there is AC loss to when a voltage goes below ATX specification. The ATX specification for the 12V rail is from 11.4V to 12.6V. So if there is AC loss and it takes a power supply 20ms until its 12V voltage gets down to 11.4V, then 20ms is the hold-up time. Some people incorrectly define hold-up time as the time between AC loss and when the power supply shuts off. This is incorrect; a power supply may actually shut itself off after hold-up time. Hold-up time is strictly the amount of time from AC loss until a voltage goes out of specification.
AC_LOSS to PWR_OK_OFF
When there is AC loss, the voltage outputs of the power supply begin to drop to lower numbers. It is the job of the circuitry of the power supply to detect this and shut off the unit before the voltages go below the ATX specification. Basically, under-voltage protection. Before any of those voltages go out of specification, the power supply is supposed to cut the PWR_OK signal. The PWR_OK signal is a cable in the main 24-pin ATX cable used to communicate with the motherboard. When on, it's telling the motherboard that its voltages are all safe. When the PWR_OK signal is cut, circuitry is supposed to shut off the power supply as fast as possible so the voltages don't go out of specification.
The latest testing methods in renowned power supply reviews are AC_LOSS to PWR_OK tests. This tests the duration of time it takes from there being AC loss to the computer dropping the PWR_OK signal. So, for example, if there is a power outage, your computer is under full load, and your power supply has an AC_LOSS to PWR_OK time of 18ms, then in 18ms your power supply will tell your motherboard, "Hey! Voltages are about to get low. Better shut me off now." And then the unit will be shut down quite rapidly once the PWR_OK signal is dropped.
There is a catch though: some power supply units drop the PWR_OK signal after the voltages go out of specification. This means when there is AC_LOSS, the power supply will continue providing the computer with energy as those voltages go deeper and deeper below the ATX specification. Once it gets to a certain low point, then it'll cut the PWR_OK signal, after harm has already been done. In a way, this is a cheating method used by power supply manufacturers to do well on old hold-up time tests that check the duration of AC_LOSS to PSU shutdown time. This cheating method is also dangerous.
EVGA G2 550 Flaw
The EVGA 550 G2 has this exact flaw. It drops the PWR_OK signal at 10.8V. This information can be found at the Tomshardware Superflower Leadex Gold 550 review here: http://www.tomshardware.com/reviews/super-flower-leadex-gold-550w-power-supply,4416-4.htm
"The hold-up time tests don't go well. Not only is the measured hold-up less than 16ms (the ATX spec's minimum), but the Power_OK signal drops after, and not before, the PSU's rails go out of spec. This means that your motherboard gets a false power-good signal from the PSU. Indeed, we measured the +12V rail floating at around 10.8V when Power_OK dropped to zero. This is a very low voltage level that applies lots of stress to the voltage regulators of components fed by +12V.
In a high-end PSU like this one, we didn't expect such nasty behavior. We have to admit that we're very disappointed by Super Flower's decision to drop the power-good signal so late, which is probably done to give the false impression that the hold-up time lasts longer. By the end of our review, this is going to cost to this PSU a lot of performance points. Whereas it might have received an award for performance, there's no way it will now."
Some of you may be thinking, "Oh, it's just 10.8V, no big deal." No, this is a big deal. Power supply experts like Aris (who did the above review) say it is a serious matter, as well as the experts on the Jonnyguru forums. It is a serious issue, and the EVGA 550 G2 should not be purchased because of it, especially in areas where there are frequent power outages.
It is important to note that Aris did do a review on the EVGA 550 G2 here, but that was before these new tests came about.
EVGA P2 Series Assumed Flaw
Most likely, the entire EVGA P2 lineup has the same issue, but right now it is merely speculation (but a pretty good one). The Superflower Leadex Platinum 550 review here: http://www.tomshardware.com/reviews/super-flower-leadex-platinum-550w-power-supply,4281-4.html
This review was before the PWR_OK to AC_LOSS tests. Hold-up time was tested to be 13.8ms. That is below the ATX specification. There is no doubt in my mind that it probably drops the PWR_OK signal at 10.8V just like the EVGA 550 G2, in order to "cheat" and get good hold-up times on the old hold-up time tests.
EVGA T2 is Safe
The EVGA Titanium lineup has been tested and does not have this issue.
EVGA G2: Rest of Lineup
As of now, the non-550W versions of the EVGA G2 lineup may have these issues, but we cannot know for sure. Power supply experts are pretty confident the rest of the G2 lineup does have this problem, which is very important.
What to do Now?
Realize that sometimes units we think are incredible really are not. Everybody likes to go around forums talking about how fantastic the EVGA G2 lineup is, but with this problem, how can it be? It shouldn't make any high tier on any list, because Superflower cheats to get good hold-up time on old tests, and sets far too low under-voltage protection values. It is a serious matter, because the VRMs of all your hardware can be seriously affected by such a low voltage, 10.8V. There is a reason the ATX specification exists. 10.8V is two times out of the specification.
I bought Evga G2 850W last year. Because it is overkill for my setup (more futureproof) and it has 10 year warranty I will have it minimum for the next 10 years. Should I be worried because of this problem? I don`t want that this to cause any damage to my components....
The EVGA G2 lineup is considered by many to be very high quality, the P2 considered fantastic, but the latest testing by professional reviewers shows that some or perhaps all of these units have a serious flaw that won't harm the PSU but could harm your other hardware. It's important to explain the concepts before anything. Very few reviewers test for this stuff - Aris, who does power supply reviews on Tomshardware and Techpowerup, very recently started a new test. This new test shows that many units have newly revealed flaws, and this problem exists with the EVGA G2 and P2 lineup. The EVGA G2 series is a direct copy of the Superflower Leadex Gold series. The EVGA P2 series is a direct copy of the Superflower Leadex Platinum series.
Old Hold-Up Time Tests
In the past, most power supply reviewers would test "hold-up time" as the amount of time from when there is AC loss (i.e. power outage) to when the unit shuts off, while under full load. For example, if a power supply is under 100% load and there is a power outage, if it takes 20ms for the power supply to shut off, it would be defined as having a hold-up time of 20ms. However, this is not an actual test with what hold-up time really is, and new tests reveal new realities. The old hold-up time tests are not in exact accordance with the definition of hold-up time.
Hold-Up Time
Hold-up time is defined as the time period from when there is AC loss to when a voltage goes below ATX specification. The ATX specification for the 12V rail is from 11.4V to 12.6V. So if there is AC loss and it takes a power supply 20ms until its 12V voltage gets down to 11.4V, then 20ms is the hold-up time. Some people incorrectly define hold-up time as the time between AC loss and when the power supply shuts off. This is incorrect; a power supply may actually shut itself off after hold-up time. Hold-up time is strictly the amount of time from AC loss until a voltage goes out of specification.
AC_LOSS to PWR_OK_OFF
When there is AC loss, the voltage outputs of the power supply begin to drop to lower numbers. It is the job of the circuitry of the power supply to detect this and shut off the unit before the voltages go below the ATX specification. Basically, under-voltage protection. Before any of those voltages go out of specification, the power supply is supposed to cut the PWR_OK signal. The PWR_OK signal is a cable in the main 24-pin ATX cable used to communicate with the motherboard. When on, it's telling the motherboard that its voltages are all safe. When the PWR_OK signal is cut, circuitry is supposed to shut off the power supply as fast as possible so the voltages don't go out of specification.
The latest testing methods in renowned power supply reviews are AC_LOSS to PWR_OK tests. This tests the duration of time it takes from there being AC loss to the computer dropping the PWR_OK signal. So, for example, if there is a power outage, your computer is under full load, and your power supply has an AC_LOSS to PWR_OK time of 18ms, then in 18ms your power supply will tell your motherboard, "Hey! Voltages are about to get low. Better shut me off now." And then the unit will be shut down quite rapidly once the PWR_OK signal is dropped.
There is a catch though: some power supply units drop the PWR_OK signal after the voltages go out of specification. This means when there is AC_LOSS, the power supply will continue providing the computer with energy as those voltages go deeper and deeper below the ATX specification. Once it gets to a certain low point, then it'll cut the PWR_OK signal, after harm has already been done. In a way, this is a cheating method used by power supply manufacturers to do well on old hold-up time tests that check the duration of AC_LOSS to PSU shutdown time. This cheating method is also dangerous.
EVGA G2 550 Flaw
The EVGA 550 G2 has this exact flaw. It drops the PWR_OK signal at 10.8V. This information can be found at the Tomshardware Superflower Leadex Gold 550 review here: http://www.tomshardware.com/reviews/super-flower-leadex-gold-550w-power-supply,4416-4.htm
"The hold-up time tests don't go well. Not only is the measured hold-up less than 16ms (the ATX spec's minimum), but the Power_OK signal drops after, and not before, the PSU's rails go out of spec. This means that your motherboard gets a false power-good signal from the PSU. Indeed, we measured the +12V rail floating at around 10.8V when Power_OK dropped to zero. This is a very low voltage level that applies lots of stress to the voltage regulators of components fed by +12V.
In a high-end PSU like this one, we didn't expect such nasty behavior. We have to admit that we're very disappointed by Super Flower's decision to drop the power-good signal so late, which is probably done to give the false impression that the hold-up time lasts longer. By the end of our review, this is going to cost to this PSU a lot of performance points. Whereas it might have received an award for performance, there's no way it will now."
Some of you may be thinking, "Oh, it's just 10.8V, no big deal." No, this is a big deal. Power supply experts like Aris (who did the above review) say it is a serious matter, as well as the experts on the Jonnyguru forums. It is a serious issue, and the EVGA 550 G2 should not be purchased because of it, especially in areas where there are frequent power outages.
It is important to note that Aris did do a review on the EVGA 550 G2 here, but that was before these new tests came about.
EVGA P2 Series Assumed Flaw
Most likely, the entire EVGA P2 lineup has the same issue, but right now it is merely speculation (but a pretty good one). The Superflower Leadex Platinum 550 review here: http://www.tomshardware.com/reviews/super-flower-leadex-platinum-550w-power-supply,4281-4.html
This review was before the PWR_OK to AC_LOSS tests. Hold-up time was tested to be 13.8ms. That is below the ATX specification. There is no doubt in my mind that it probably drops the PWR_OK signal at 10.8V just like the EVGA 550 G2, in order to "cheat" and get good hold-up times on the old hold-up time tests.
EVGA T2 is Safe
The EVGA Titanium lineup has been tested and does not have this issue.
EVGA G2: Rest of Lineup
As of now, the non-550W versions of the EVGA G2 lineup may have these issues, but we cannot know for sure. Power supply experts are pretty confident the rest of the G2 lineup does have this problem, which is very important.
What to do Now?
Realize that sometimes units we think are incredible really are not. Everybody likes to go around forums talking about how fantastic the EVGA G2 lineup is, but with this problem, how can it be? It shouldn't make any high tier on any list, because Superflower cheats to get good hold-up time on old tests, and sets far too low under-voltage protection values. It is a serious matter, because the VRMs of all your hardware can be seriously affected by such a low voltage, 10.8V. There is a reason the ATX specification exists. 10.8V is two times out of the specification.
I bought Evga G2 850W last year. Because it is overkill for my setup (more futureproof) and it has 10 year warranty I will have it minimum for the next 10 years. Should I be worried because of this problem? I don`t want that this to cause any damage to my components....
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