(Faulty?) Soft power switch caused resume from sleep failures

When the motherboard (or ‘mobo’) in my ‘media’ PC stopped working recently, I decided to turn lemons into lemonade and use it as an excuse to build a Home Theatre PC for my living room. While I was deciding on which HTPC case to buy, I installed the new motherboard in my old case to test it out.

My original media PC used to frequently fail to resume from sleep while unattended (e.g. waking up to record a TV show). It would just continually initialize the DVD drive and the hard drive light would flash on and off. I had tried changing just about everything to resolve this problem (power supply, graphics, memory). In the end suspected it was either the mobo or the processor. As a workaround, I configured the machine to bypass S3 sleep and go straight to S4 hibernate, which while it worked, was slow compared to S3 sleep and made for a long wait when firing up the XBOX 360 in Media Center extender mode.

I figured that I had a good chance of resolving this problem for good with the new mobo. For a short while things looked promising, but it wasn’t long before I noticed the same failure as I’d seen with my old mobo!

Given that the processor was also new, all signs pointed to the case. There really wasn’t anything special about it (e.g no media readers, or other onboard goodies except a couple of front USB connections). So on a hunch, I swapped the power and reset connections on the motherboard so that the reset button would power on the machine instead.

My new (temporary) setup never experienced any resume from sleep failures after that (I also ran the system through about 1000 sleep/resume cycles using pwrtst.exe from the Windows Driver Kit to make sure). What was odd is that I’d never experienced any problems when manually resuming from sleep, so I have no idea how the power switch was randomly interfering with unattended wake.

And at the end of the day, I don’t really care now that S3 sleep is working reliably!

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