What's off when it's off!?

[SpellowHouse]

Can anyone tell me how a modern PC power supply works...what is off when the PC is in standby?

I know that when powered down that some motherboards maintain some functionality, so there must be some power-lines still active, but surely some must be physically off, such as the SATA power connectors?

The reason I am asking is because I want to "sense" the state the PC is in, and it seems to me that monitoring the SATA power lines from the PSU is one possible answer.

 

[jp7152]

I think it might be more down to your choice of CPU and the power settings you have enabled in BIOS. If i understand correctly there are different levels of standby. A more modern system may be able to 'turn off' more parts of the system.

Also it might depend how Windows is configured. I am not sure if it will be useful or not but there is a program called Power Settings explorer and it allows you to see and adjust a lot of normally hidden power settings. I think SATA power might be part of that also. You can google "Windows power plan settings explorer utility" if you want to take a look at it.

 

[Tetras]

Can anyone tell me how a modern PC power supply works...what is off when the PC is in standby?

Afaik, it uses the rail: 5VSB and the motherboard decides what devices to power when the PC is off.

it seems to me that monitoring the SATA power lines from the PSU is one possible answer.

I don't think SATA devices should be powered when the PSU is off.

 

[SpellowHouse]

I don't think SATA devices should be powered when the PSU is off.

Exactly. So my thoughts are that I will monitor the SATA lines. It's an easy one to do because of course STATA power connectors are easy to obtain, so all I need to do is buy a SATA power extension and clip the male plug off and BAM there are the wires to connect to!