sharing a power supply

Alan Ward award at
Fri Jul 4 03:53:52 EDT 2003


En/na Andrew Piskorski ha escrit:
> Alan, how did you go about attaching three motherboard connectors to
> that one 450W supply?  Where'd you buy the connectors, and did you
> have to solder them on or is there some sort of Y type splitter cable
> available?

I started with dominoes, and when I was sure it worked soldered them.
Jack Wathey posted the following:

 >> Rather than cut up the wires
 >> of a power supply, I cut up the wires of extension cables:

Being in southern Europe, there's no hope of getting these here.
But busted power supplies (for parts) are easy to find :-(

> Also, did you do anything to get the three slaves to power on
> sequentially rather than all at once?  Or are you just hoping that the
> supply will be able to handle the peak load on startup?

Can't do anything about that. When the supply goes on, it powers the
boards, and they start up, period. Maybe a breaker on the 5V and
3.3V lines would be a solution.

However, I reason the following: power-on spikes come from condensators.
But there are a lot more condensators in the power supplies than on
the motherboards - at the very least a factor of 100 more in capacity.
So I expect the spikes on the AC circuit as the supply is getting
charged up, rather than on the DC part.

(Comments, Alvin, Jack?)

> In my limited experience with Athlons, I've seen cheap power supplies
> cause memory errors.  (In my case, only while also spinning a hard
> drive while compiling the Linux kernel; memtest86 did not cach the
> problem.)  So I'd definitely be inclined to try using one high quality
> supply rather than three cheap ones.  But until your emails to the
> list though I hadn't heard of anyone doing it.

There seem to be two-stage power supplies for racks: a general 230V / 
12V converter for the whole rack, plus a simplified low-voltage supply
for each box. I've never even seen any of these around here, though.

What I'm doing is not strictly COTS. I loose the advantage of just
plugging the hardware in and worrying *only* about the soft ...

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