Question Almost borked my system with "Deep S5 Power Policy." What is it?

mikewinddale

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Dec 22, 2016
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So I just almost borked my system, and I'm not sure why. Long story short: enabling "Deep S5 Power Policy" in my BIOS rendered my system unbootable and then caused a cascade of other problems. But I can't find anything online about "Deep S5 Sleep," so I'm not sure why I got these problem.

Motherboard: Supermicro M12SWA-TF (ThreadRipper Pro WRX80 platform)

Long story:

My motherboard's BIOS contains a setting called "Deep S5 Power Policy," with options to enable or disable. The default is disabled. Now, I know that "S5" is the technical name for the shutdown state.

So I wondered, "What's deeper than shutdown?" But the BIOS manual didn't explain this option. So I thought I'd turn it on and find out. What's the worst that could happen?

Well, when I turned on my computer, the CPU thermal diode reported a null value.

Or more precisely, the CPU thermal diode was directly reporting a value, but the BMC was reporting a null value. On this particular motherboard, the BMC controls and monitors the thermal sensors, and it also controls the fan RPMs.

The fact that the BMC was failing to report the temperature that was being reported by the CPU thermal diode meant that my CPU fan would no longer adjust its RPM to match the CPU temperature. Indeed, I turned on Prime95 with 1 core, and my temperature quickly throttled up to 75C, but the fans did not speed up. (Again, the CPU diode was directly reporting, but the BMC was showing a null CPU diode. So I knew the CPU was 75C, but the BMC didn't know.) So I knew that if I ever ran intensive software again, I might fry my CPU.

I rebooted to see if the BMC's reporting would turn back on. But no, when I finished rebooting, the BMC's reporting of the CPU thermal sensor was still null.

I Googled, and some people suggested resetting the BMC.

After I reset the BMC, I was locked out of the BMC. When I pinged its IP address, I was met with no response. And when I rebooted the computer, I was met with a completely blank screen. I turned the computer on and off a few times, and every time, I was met with a blank screen.

So then I reset my BIOS by removing the coin cell battery and bridging the contact.

When I turned on my computer, I was met with the normal screen. Hooray! And then it booted into Windows. Double hooray!

But when I restarted my computer from within Windows, I got a Blue Screen of Death: POWER_STATE_FAILURE. Typically, this indicates a problem with a software driver or with a physical device, so the remedy is to reinstall the drivers, and to remove any new hardware devices that have been recently installed.

I knew I hadn't installed any new hardware. But I thought, maybe the motherboard is being funky, what with everything that just happened. So I uninstalled and then reinstalled the chipset driver, without rebooting in between. When I rebooted the computer, it finally reboot successfully.

All of this because I tried out a BIOS setting called "Enable S5 Deep Sleep."

So can anyone here tell me what the heck just happened???!!!
 
Last edited:

mikewinddale

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Dec 22, 2016
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Incidentally, I did discover that I can't use sleep mode on this computer. Whenever I do, all of the thermal sensors - not just the CPU thermal sensor - report null values, and the fans spin at their minimum RPM regardless of the computer's activity. But rebooting the computer fixes the problem.

I reported this to Supermicro, and they replied that this is normal. The BMC activates the sensors during POST, so when you put the computer to sleep, the BMC loses the connection with the sensors, and it cannot resume connection until the computer POSTs again.

This seems like a problem to me, but what can I do? Maybe I should have bought the Gigabyte or Asus WRX80 motherboard, but I bought what I bought.
 

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