Dyson Poindexter

Hello there,

I'm wanting to power up my hard drives and fans before I turn the system on. I'd like to disconnect /PS_ON from the ATX connector, and wire it to a switch. This way, I can bring my drives up without booting the system. My only concern is whether or not it will damage the motherboard by being powered when it's not expecting to be.

Also, could I instead abstract PWR_OK to a switch? The ATX spec states that a board must wait for PWR_OK in order to boot. What is the typical behaviour of a board whilst in this wait state?

Regards,

Dyson Poindexter

shinji2k

Using a switch on the PWR_ON circuit will indeed turn on the PSU and power your HDDs. Merely applying a voltage to the motherboard will not do any damage. If the mobo isn't turned on it won't draw any current. You should be able to just hit the case power button and turn the mobo on if the PWR_ON circuit has already been tripped. I haven't tried this though.

__________________
Pearl in the Rough (My on going case mod comp project that I couldn't finish on time)
Actual Power Consumption of a few components I own *Updated 12/04 with 5870 Results*

Please forgive me, I have SIWOTI syndrome.

A still more glorious dawn awaits. Not a sunrise, but a galaxy rise. A morning filled with 400 billion suns. The rising of the Milky Way.

Dyson Poindexter

I was assuming that, though I imagine it could be confusing to a motherboard to be powered if it's not expecting it. I'd likely have to look at how the starting circuit jives with +5VSB to see what exactly will happen. Either way, it will likely be entertaining.

Regards,

Dyson Poindexter

shinji2k

The 5VSB is always on, no matter what. The way I understand ATX spec, is that when the power switch on the mobo is tripped it starts a sequence. First it will trip the PWR_ON circuit, turning the PSU on. Then it will test the PWR_GOOD circuit to make sure the PSU turned on. Then it will go into it's boot procedure. Tripping the PWR_ON circuit to turn the PSU on first shouldn't affect the rest of the boot sequence. But like I said, I haven't tested this personally nor have I seen anyone else do it. Why do you want to turn the fans and HDDs on by themselves?

__________________
Pearl in the Rough (My on going case mod comp project that I couldn't finish on time)
Actual Power Consumption of a few components I own *Updated 12/04 with 5870 Results*

Please forgive me, I have SIWOTI syndrome.

A still more glorious dawn awaits. Not a sunrise, but a galaxy rise. A morning filled with 400 billion suns. The rising of the Milky Way.

Dyson Poindexter

I'd like to lessen the startup-load on the PSU, and also I plan on adding a mini-itx "co-computer" that serves as a router/server, and it will be powered from the +12V line, going to a pico-psu.

Dyson Poindexter

I forced /PS_ON by jamming a wire into the top of the 24-pin connector, with the computer off. The computer's fans spun up (albeit not at 100% as expected, maybe 25% for both cpu and gpu) and about 30 seconds later, the computer booted. Interestingly, when I removed the wire jumper, the computer shut down. It seems forcing the PSU on messes with the mobo's own PS_ON pulldown. I'm going to continue my research by experimenting with PWR_OK to try to keep the board from turning itself on.

Regards,

Dyson Poindexter

shinji2k

If you take the PS_ON pin out of the connector it should work better.

__________________
Pearl in the Rough (My on going case mod comp project that I couldn't finish on time)
Actual Power Consumption of a few components I own *Updated 12/04 with 5870 Results*

Please forgive me, I have SIWOTI syndrome.

A still more glorious dawn awaits. Not a sunrise, but a galaxy rise. A morning filled with 400 billion suns. The rising of the Milky Way.