Ancillary power supplies

[cheesehead]

High-grade medical surplus power supplies are extremely cheap - $30 will get you one capable of providing a 20A into 12V plus 12A into 5v, perfect for powering disk drives, fans, and all the power-hogging electronics off of your motherboard. A similar setup might be used for powering a power-hungry PCIe video card.

Has anyone tried this?

 

[mpilchfamily]

With only 4V and 5V you are not taking anything off the PSU. All fans and drives use 12V as there primary voltage. Besides the fans, HDD, and optical drives are a very spall percentage of your PC's power usage. The CPU and video card are nearly 75% of the system's power draw.

now high end system have been run off 2 or more PSUs. You can get a plitter that allows up to 4 PSUs to be used in a single system.
http://www.frozencpu.com/produ...-XSU-BL.html?tl=g11c28

Then there are suplamental PSU like these that are for powering the video card to help releive that load off the system.
http://www.newegg.com/Product/...x?Item=N82E16817104019

but for a few more $$ you can get a single PSU to power the whole system.

 

[zerocool84]

$64 just for a "videocard" power supply??? Damn what a rip.

 

[cheesehead]

Oops...typo. It was supposed to be 20A into 12v - more than enough for a pair of all but the biggest video cards.

 

[Modelworks]

I prefer not to use a extra supply unless that supply was designed for it.
Most ATX power supplies are not designed expecting there to be another supply installed and so the regulation isn't expecting another voltage source. In theory it is possible to have a situation where the voltage from one supply is being summed with the second supply allowing neither supply to properly regulate the voltage it outputs.
Supplies that are designed for use with multiple supplies take that into account in the design.

 

[cheesehead]

Originally posted by: Modelworks
I prefer not to use a extra supply unless that supply was designed for it.
Most ATX power supplies are not designed expecting there to be another supply installed and so the regulation isn't expecting another voltage source. In theory it is possible to have a situation where the voltage from one supply is being summed with the second supply allowing neither supply to properly regulate the voltage it outputs.
Supplies that are designed for use with multiple supplies take that into account in the design.

I can see how this might theoretically be a problem, though from my (admittedly very limited) experience building power supplies, I'm not sure how. Does anyone know if the 12v connector on PCIe cards is connected to the 12v leads on the PCIe bus?

Also, an ancillary PSU would work perfectly for powering fans, optical drives, and hard drives - all of which are effectively isolated from motherboard power.

 

[mpilchfamily]

The 12V PCI-e power is not tied into the 12V lines on the PCI-e slot. The only place you have to worry about cross voltages like that is with the CPU and motherboard. The CPU and motherboard connectors should come from the same PSU. All other items you don't have to worry about.

 

[Rabbits]

It's really not a necessity unless your worried about your PC shutting down because you have less power.