ATX & AT in one system, questions.

I'm thinking of running all my cooling gear for my main rig (and possibly the server if I go for a twin-rig watercooling setup) on an AT power supply.

I have recovered one from an old system, it's rated for 4.5A on the 12v rail and 18A on the 5v rail. Questions:

• Can I run the power supply loaded on the 12v rail but no load on the 5v rail?
• I may be running 4*700mA fans, 6*100mA fans and possibly a mini-fridge requiring 2-3A. Is overloading the 12v rail totally inadvisable with no loads on other rails?
• If overloading single rails isn't possible, can the 5v rail be uprated to 12v somehow or would getting a better PSU be worth it?

More questions later, thanks in advance for now

The older power supply can't do that. You can't milk more than it can produce. Anyway, approaching the maximum load will lower the voltage. Also the psu will die, guaranteed, if you connect all that stuff to it. Having no load on the other rails doesn't matter. Why don't you just pick up a cheapo psu.

Trying to run 6.4 amps on an ancient psu spec'd to only 4.5 amps is obviously a bad idea. Just running your fans would be pushing it. You never want to fully load it.

Quailane said:

approaching the maximum load will lower the voltage.

Click to expand...

Yeah, the old internal resistance chestnut.

Also the psu will die, guaranteed, if you connect all that stuff to it.

Click to expand...

Was thinking that but was wondering out loud. The fans will probably be connected through a fanbus but I'm not sure how it regulates the power going to the fans. I know that some of the more powerful fans can be connected to a thermistor or a variable resistor but if they are connected straight to the fan then they are regulated via PWM. I'm not sure if the fanbus does so in the same way, because if it does, couldn't the momentary high current short the PSU or will it absorb fluctuations?

Why don't you just pick up a cheapo psu

Click to expand...

The AT psu happened to be hanging around, plus I like the whole "manualness" of the thing, like how it has a directly-connected power switch for one. That said, if this doesn't work I may mod-up a decent ATX psu but I'd rather get this going. There would be other considerations if I used an ATX, I'm pretty sure they need a minimum load....

Having no load on the other rails doesn't matter.

Click to expand...

Cool.