Hold-Up Time

Hold-up time represents the duration for which a PSU can maintain stable output as defined by the ATX specification without input power. This is very important when the quality of your electricity varies, and there are short drops in the supply (dips or brownouts).

In the oscilloscope screenshots below, the blue line is the AC input mains signal, the green line the "Power Good" signal, and the yellow line the +12V rail. The measured timing variable is listed as ΔX.

Hold-Up Time

AC Loss to PWR_OK Hold-Up Time

PWR_OK Inactive to DC Loss Delay

Hold-up time is right at 17 ms, and the power ok signal is accurate, but below 16 ms.

Timings for Alternative Low Power Modes (ALPM)

Traditionally, sleep mode (S3) shuts the system off for a long time (minutes or hours) to reduce power consumption. However, this approach adds a few seconds of delay when resuming from standby. Microsoft recently introduced Modern Standby, which brings the instant-on capability to PCs—just like your phone instantly turns on without any noticeable delay. Modern Standby builds on the Alternative Low Power Modes (ALPM) capability Intel has defined. To support ALPM, a power supply must wake up from sleep quickly to ensure system stability—think of it as the PSU's boot time.

We measured T1 and T3 for the reviewed PSU at 20% and 100% load.



Power-on time is well below 100 ms, so the PSU won't have any problem with mainboards. Moreover, the PWR_OK delay is below 150 ms, so the PSU supports Alternative Low Power Modes.