[vox-tech] more adventures with power supplies

[Jonathan Stickel]

In my haste to replace my blown computer 
(http://lugod.org/mailinglists/archives/vox-tech/2007-01/msg00045.html), 
I bought a no-frills Compaq desktop (Presario SR1917CL) for cheap.  I 
also wanted a Nvidia graphics card to play some games, and chose the PNY 
GeForce 7600 GS, mainly because it seemed to have the highest 
performance to power use ratio.  The box spec'd a 300 W PSU minimum for 
the single card.  This is what the PC had, and so I thought I would be 
OK.  Although PSU total wattage suggestions of many high-end Nvidia 
cards aren't too bad (400-500 W) many have 12 V requirements of 20 A or 
even much higher.  Browsing at Frys, I had a hard time finding any 
reasonably priced PSU that gave more than 18 or 19 A on the 12 V power 
channel.

I plugged in the graphics card, and everything seemed to be working 
great, at least in Windows.  While installing Linux (Gentoo), however, 
the SATA hard drive would very occasionally stop communicating.  This 
made me concerned, but memory testing and various hard drive tests all 
passed.  Now the most interesting part:  my self-built kernel, without 
an initrd, would not boot, no matter what I tried!  The auto-generated 
kernel with an initrd would boot OK.  Again, the graphics card was 
operating flawlessly, now in Linux.  Finally, suspecting inadequate 
power, I pulled the graphics card.  Sure enough, the hard drive issues 
went away, and even my self-built kernel would boot!  I thought this was 
quite interesting; somehow the hard drive power needed when booting 
without an initrd was enough to cause a failure.

I immediately went out and bought a better power supply (Antec 650 W, 19 
A on the 12 V loop), and everything is working together just fine now. 
Hopefully this will help and warn some of you about power requirements 
of Nvidia graphics cards.  While it is tempting to get the latest and 
greatest card, beware of the cost of replacing your power supply too!

Regards,
Jonathan