What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Hold-up time is how long a power supply unit (PSU) keeps its DC outputs within specification after AC input is interrupted. Power Good (PWR_OK or PG) is a logic signal that tells the motherboard when the PSU’s key outputs are in range—and warns it before they can no longer be guaranteed. Hold-up time is stored-energy ride-through, not backup power; PWR_OK is a status signal, not a source of power.
What hold-up time means
A PSU stores energy, principally in its input capacitors, so it can continue delivering regulated DC for a short time after incoming AC disappears. Hold-up time is the interval during which those outputs remain within their specified limits. It is meant to bridge brief interruptions, such as a missed AC cycle or the transfer time of some UPS units, not to keep a computer running through a sustained outage.
The figure depends on the PSU’s input voltage and frequency, output load, and the test conditions used. A hold-up-time number without those conditions is difficult to compare with another PSU’s figure.
What the PWR_OK signal tells the motherboard
Intel’s 2023 ATX Version 3 Multi Rail Desktop Platform Power Supply Design Guide defines PWR_OK as a signal the PSU asserts high when the +12 V, +5 V, and +3.3 V outputs are within their regulation thresholds and the converter has enough stored mains energy to guarantee continued operation within specification for the required duration. If a monitored rail drops below its threshold, or AC has been absent long enough that operation can no longer be guaranteed, the PSU deasserts PWR_OK low. The motherboard can use that warning for shutdown or reset handling before the DC outputs are lost.
#1 Best Overall
- [8-in-1 ATX Power Supply Tester] -- Support test 20-pin ATX / 24-pin ATX / HDD (IDE) / Floppy 4-pin / PCI-e 6-pin / 4-pin / EPS 8-pin (NOTE: can not fit for PCI-e 8-pin) / SATA connectors
- [Aluminum Alloy Enclosure] -- Light and Easy to Carry, High Strength, Nice Thermal Conductivity & Corrosion Resistance
- [1.8'' LCD Screen] -- Outputted Voltages shows on the 1.8'' LCD Screen, Easy to Read ( The 1.8'' LCD Screen was Powered by 20-pin / 24-pin Connector ), Note: The Product Screen Has a Load of Scratches All Over It？Because The Screen is Easy to Scratch, We Put a Protective Film on It, If You Think It's Not Beautiful, You Can Tear It Off by Yourself
- [Beep Alarm] -- When your power supply test value is beyond normal range, the Power Supply Tester would issue a buzzer alarm, Easy to Know
- NOTE: The voltage of 20pin / 24pin connectors is displayed by the LCD Screen, as "+3.3V", "+12V1", "+5V", "-12V", "5VSB", "PG" (except "+12V2" on LCD Screen); The voltage of PCI-e 6P / 4P / EPS P8 connectors is displayed by the LCD Screen as "+12V2"
PWR_OK is a digital interface, not extra stored energy. Intel lists it as +5 V TTL-compatible. ATX 3 and ATX12VO tables specify a low level below 0.4 V, a high level from 2.4 V to 5 V, a 1 kΩ high-state output impedance, and maximum ripple/noise of 400 mV peak-to-peak. These are interface limits for system design; they do not establish measured performance for any particular retail PSU.
How long should a PSU hold up?
There is no single millisecond figure that applies to every ATX revision and load. Intel’s 2023 ATX12VO guide gives different values for full-load hold-up and also distinguishes total output hold-up from the PWR_OK warning interval. Intel’s older ATX12V Version 1.1 guide specifies another condition. Compare figures only alongside their specification revision and test load.
Rank #2
- LCD DISPLAY: LCD liquid crystal display, the output voltage is clear at a . If there is any defect, the buzzer will automatically alarm.
- VOLTAGE DISPLAY: It can also measure the output wire P4/P6/P8/SATA/IDE, and the external DIE/SATA/P6/P8 is the light display, there is no LCD voltage. There is LCD voltage display only when connecting to the 24pin or 20pin.
- MINI and PRACTICAL: Now the number of power output groups is increasing. As long as one of them has problem, the hardware of the computer system may work abnormally or even burn out. To measure whether the output voltage output of the power supply is stable, the player usually uses a multimeter. But for the average user is still a little troublesome.
- ATX POWER SUPPLY TESTER: We have developed a portable computer power tester for the power supply market that cannot judge the quality of the power supply. It has LCD intuitive and accurate display voltage (+/-0.01V), automatic fault alarm, complete test interface, small and beautiful appearance, and more test functions. It is your best choice and helper to quickly detect PC power.
- WIDE APPLICATION: ATX Power Tester is a powerful power test device that can detect ATX, BTX, ITX, TFX computer power supplies, and can display various groups of voltage and PG values in the LCD screen, and quickly detect computer power supply to facilitate the instrument.
| Specification and condition | Published timing | What the figure describes |
|---|---|---|
| Intel ATX12VO, 2023 | 12 ms at 100% full load (required); 17 ms at 80% full load (recommended) | Hold-up time at the stated load |
| Intel ATX12VO, 2023 | T5: greater than 11 ms required and greater than 16 ms recommended | PWR_OK hold-up interval |
| Intel ATX12VO, 2023 | T6: greater than 1 ms | Delay from PWR_OK becoming inactive to DC loss |
| Intel ATX12V Version 1.1 design guide; publication year not stated in source metadata | 17 ms minimum at maximum continuous load | Hold-up time |
| Intel ATX Version 1.1 design guide; publication year not stated in source metadata | PWR_OK delay: 100–500 ms; rise time: no more than 10 ms; power-down warning: at least 1 ms | Signal timing |
The ATX12VO table separates total hold-up (T5+T6) from the PWR_OK warning interval. The signal transition is therefore not the same event as complete DC output loss. Do not treat timing values from different revisions, loads, or timing definitions as interchangeable.
Free tools Windows power users keep installed
One-click scans. No signup required.
Quick Recap
Rank #4
- The LCD power tester is a powerful power test device. This power tester only needs to be connected to the ATX connector of the power supply to easily and intuitively know whether the output of each power supply is normal. It can detect ATX, BTX, ITX, TFX computer power supply, and can display various voltage and PG values in liquid crystal to quickly detect the performance of computer power supply.
- The LCD displays various parameters such as output voltage and PG. When each parameter exceeds the normal value, the buzzer will sound a warning and the corresponding value will flash.
- It can measure the voltage of each group of power supply 3.3V/+5V/+12V/-12V/SB+5V/PG, and also measure the output wire P4/P6/P8/SATA/IDE, external DIE/SATA/P6/P8 is the light Displayed, there is no LCD voltage. Only the 24pin or 20pin will have the LCD voltage.
- It has LCD intuitive and accurate display voltage (+/-0.01V), automatic fault alarm, complete test interface, small and beautiful appearance, and many test functions. It is the best choice for quickly detecting PC power.
- Support 20Pin, 24Pin ATX interface / SATA interface / 4Pin, 8Pin interface / PCI-E graphics card 6Pin interface / floppy drive interface / ATE hard disk interface.
Rank #3
- 【Right Tool for the Job】A great addition to any tool kit for someone working on a PC. The Dr. Power III Pro can check a connection for continuity, provide real-time voltage and PG readings, and alert for detected faults with audible and display alerts.
- 【Real-Time Data】Capable of delivering real-time data for +12V, +5V, +3.3V, and +5Vsb outputs as well as providing a PG (power good) signal measured in ms (milliseconds) for help identifying issues with power supplies.
- 【PCIe Gen 5.1 Sense】Able to detect the the sideband SENSE0/SENSE1 signals for the correct identification of power able to be delivered (150W, 300W, 450W, 600W) to a modern GPU.
- 【Fault Warnings】 Easily identify issues thanks to the active alert system, able to alert the user with both an audible beep to draw attention along with the display turning red and indicating where the fault was detected.
- 【Color Display】On top of being updated to test the newest ATX 3.1 v3.1 spec PSUs, the Dr. Power III Pro also brings a color screens for some extra eye grabbing notifications.
What to check in a PSU specification
- ATX revision: Identify whether the stated requirement is for older ATX12V, ATX 3.x, or ATX12VO; revisions can define different timing and test conditions.
- Load at measurement: Check whether hold-up is reported at 100% load, 80% load, or another specified level.
- Input conditions: Look for the input voltage and frequency used for the measurement.
- PWR_OK timings: Check the signal delay, rise time, and AC-loss warning interval as well as total hold-up.
- Published evidence: Prefer a manufacturer datasheet that gives measured timing data and tolerances over an unlabeled marketing claim.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
