Thursday, July 7, 2011

The case of the crashing computer

Recently I upgraded my main system to use dual monitors. This can be of great help when developing software. But ever since adding the second monitor, my machine would experience random crashes - about once a day. But these crashes weren't the usual BSOD that occur in Windows, instead both monitors would go blank and the computer would half power itself off. It was like the machine entered standby, except it would not wake up. If you pressed the reset button the machine would power off (huh?).

I quickly ruled out a Windows software problem. A driver crash almost always results in a BSOD which wasn't occurring. So I started to look at the hardware. I suspected the motherboard, RAM, or video card. But how do I find out what? I checked the BIOS event log... nothing. I tried leaving the second monitor off, but it still crashed. My next guess was perhaps the power supply. When a second monitor the video card should use more electricity, and maybe if it used too much electricity the power supply couldn't keep up. My machine has a 400W power supply which should be more than enough.

Then I remembered my computer has an "automatic voltage regulator," specifically the APC Line-R 600. An automatic voltage regulator is like a surge protector in that it prevents over-voltage, but it also protects the system against brief brown-outs and black-outs. It is not a battery backup unit, but it does some of the same. So I tried replacing this unit with a normal surge protector and wouldn't you know it, the crashes have gone away!

So apparently my computer and two monitors could pull just enough energy from the unit to cause it to crash my system.

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