Does a PC need to use 100% of the total watts necessary for all devices at boot up?

[Petros_K]

In other words, if your system and the devices connected to it require 300 watts of power to run, at boot up your system will draw 300 watts of power immediately from the power supply unit. Is this true?

 

[alphadogg123]

No a computer only draws as much power as it needs. At startup a computer draws significantly more power than at idle since it is loading files from its storage medium into ram and doing a bunch of other things. Under full load the latest haswell system only uses 100w (http://www.eurogamer.net/articles/digitalfoundry-haswell-core-i7-4770k-review) but this number can shoot up depending on your computers components and your cpu speed.
Google system power under full and idle loads if you want more info

 

[Petros_K]

No a computer only draws as much power as it needs. At startup a computer draws significantly more power than at idle since it is loading files from its storage medium into ram and doing a bunch of other things. Under full load the latest haswell system only uses 100w (http://www.eurogamer.net/articles/digitalfoundry-haswell-core-i7-4770k-review) but this number can shoot up depending on your computers components and your cpu speed...

This is a yes or no type question. I have someone telling me that upon powering up as the computer loads the OS a) all installed devices will power up at the same time including all drives (optical and hard drives), the motherboard components, and all other devices such as video and PCI cards, and b) each device will require 100% of the recommended wattage for the device, and c) if you do not have a power supply unit that will provide the total wattage needed for all devices to boot at the same time this way your power supply unit is likely to fail or fry. Someone even told me that the motor for a hard drive requires THREE TIMES the estimated power for normal running. IS ANY OF THIS TRUE?

 

[hunter315]

The bit about hard drives is true, start up currents on motors are far higher than steady state power draws, large servers can have their drives arranged for "staggered spin up" which means that they start up one at a time rather than resulting in a large power draw all at once.

Your CPU and GPU do not require their peak power, they are running much higher than their idle power levels, but unless you actually have them doing something most of their transistors are sitting there doing nothing and not consuming much power at all. Though for most systems with PSU issues you will find them at startup as it is likely to bring systems that aren't used at maximum load normally to their "peak" power, which is still well below the maximum possible power consumption; they will only need it for a very short time though and most PSUs can provide a higher amount of power for a short "peak" draw. If start up is going to cause your PSU issues, so will heavy use after booting up but it is easiest for people to blame it on the booting up rather than the POS PSU.