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Author Topic: Seperate 12 volt power supply for multiple rigs.  (Read 1064 times)
rotrot
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January 16, 2012, 12:59:30 AM
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I'm preparing to setup several rigs and I'm wondering if there is any reason why I couldn't get a single 12v high-amperage industrial power supply and run all of the cards off of it allowing me to use normal power supplies for each of the rigs. Has anyone thought of doing this? Any reason why it wouldn't work? Problems?
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jake262144
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January 16, 2012, 02:08:08 AM
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[executive summary]
I strongly advise you to abandon your plan of going with a non-standard power supply.
You're with all likelihood making a serious mistake which will cost you dearly.

[technical explanation]
Your industrial power supply would have to strictly conform to the ATX specification to be compatible with the computer hardware.
Since it was never built for powering PCs, there is no reason whatsoever why it would be.
A heavy-duty industrial power supply might not even be a regulated power supply, much less PC-grade.


An ATX power supply must meet some very strict criteria:
(1) all the voltage rails (in your case just 12V) must never deviate by more than 5% from their nominal values at any load,
(2) electric noise and/or ripple may never exceed 120mV,
(3) upon start-up, the transient voltage when the rails are becoming ready must not exceed their nominal voltages by move than 10%,
(4) those power rails must become fully ready in 1020ms (the rising edge of the transient voltage may not be longer than 1020ms).


All of these potential failure points have very serious implications for the well-being of your hardware.
Failing even one aspect of the specification might at best result in unstable work or failure to start at all. At worst, you will fry your machine and possibly your new power supply with it.

You'd have to consult with the manufacturer (someone technical, like an engineer involved in product development) and ask them about compliance with ATX spec.
You will get no written guarantees, however, and if you damage a whole rig-full of expensive GPUs there will be no one to reimburse you.


If you decide to follow your plan (which I suggest you not do), please test that power supply on some junk-pc you won't regret killing.
The test should last at least two weeks and significant loads would have to be applied. You will have to find some way of creating those test loads.
I won't even go into wiring that thing up properly and clamping all the connectors.


There was a very similar case here with someone burning two FPGA boards (ZTEX boards, I believe) with a crappy, non-regulated power supply.
The nominal voltage was 12V but transients had to be at least 18V because the 16V-rated VRMs burned in seconds. Needless to say, that failure was not covered by the warranty and that individual could by no measure be called a happy camper.
DILLIGAF
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January 16, 2012, 02:25:53 AM
 #3

I'm preparing to setup several rigs and I'm wondering if there is any reason why I couldn't get a single 12v high-amperage industrial power supply and run all of the cards off of it allowing me to use normal power supplies for each of the rigs. Has anyone thought of doing this? Any reason why it wouldn't work? Problems?

If you need the extra power as it seems you do then you can get an adapter cable for the 24 pin connector on the mother board that will allow it to turn on two power supplies when it is started giving you the option of using two normal PC power supplies to power all the cards and the motherboard at once.
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January 16, 2012, 03:18:25 AM
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You likely find that a single massive industrial power supply will be more expensive than mass produced ATX power supplies.  When you add the cost and complexity of custom cables, the risk in regulation and ripple it makes it even riskier.
jake262144
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January 16, 2012, 06:09:58 AM
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... When you add the cost and complexity of custom cables, the risk in regulation and ripple it makes it even riskier.
And timing. Mind you DAT, timing is a crucial but is a very little known parameter as it's not measurable without a spectroscope.
Like I said, on machine startup the PSU has 10 milliseconds to sort its voltages out. If the industrial one achieves stable power levels in 50 ms, the rig is certainly not going to work.
rotrot
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January 16, 2012, 06:53:52 AM
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Wow, thanks for the great advice. I guess Ill just need to spend the extra cash on 1200 watt power supplies. I really wasnt able to find much information online and I had assumed that as long as the voltage was correct and there was sufficient amperage available it would work. Im glad I asked.
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January 16, 2012, 06:55:18 PM
 #7

I think it'd work. If you hook a 900W to your graphics cards and run the mobo off a 200W I think you should be good.
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