iMac with 10.15 Catalina can't disable power nap?

[Makosuke]

I went through all the sleep problem reports on this forum but none seem to fit mine. My week-old iMac (2020) on 10.15.7 is not having problems going to sleep, and it's not waking and staying awake, but it is behaving like I've got Power Nap enabled even though I don't.

Specifically:

• Put iMac to sleep.
• iMac sleeps.
• Some time (~1 hr?) I hear external drive fans spin up like the iMac woke, although the screen doesn't come on.
• About a minute later, back to sleep.
• Repeat some indeterminate amount of time (~1hr?) later.

I've periodically fought with my previous iMac not wanting to stay asleep, but this is different. I have Power Nap turned off, wake for network access turned off, no schedule. Wake for Bluetooth is on (kind of has to be to make the keyboard wake it), but that can't be the cause or the screen would be coming on and it would stay awake.

Peripherals are an Apple keyboard and trackpad, a Logitech mouse running off Unifying dongle, a Thunderbay Mini and M2, and a USB hub with nothing plugged into it. I can't see how it could be the mouse, any other USB device, or the Thunderbolt drive enclosures, because if it was the screen would wake and it would stay awake instead of going back to sleep a minute or so later. It could be the Thunderbays randomly waking up on their own, but as far as I know they never did that before so I'm assuming not.

Anybody seen this?

 

[frou]

Sounds very much like an issue where eGPU fans spin up. I posted a solution here:

https://forums.macrumors.com/threads/catalina-egpu.2193797/post-29003536

 

[Makosuke]

Interesting. Seems quite likely that this is the cause, since these are basically external PCI enclosures that only host drives.

I don’t believe I need multicast advertising for my network setup, so I’ve changed that setting, we’ll see if it was indeed the cause (or if there was something going on with Apple device intra-communication that I wasn’t aware of that this breaks).

Thanks for the tip!

 

[Makosuke]

Or maybe not... I haven’t sat in the room when not using the machine for an extended period yet, but I caught it doing the same thing at least once after running that command, and confirming that NoMulticastAdvertisements is set to “1” .

It just now occurs to me that I might need to reload mdnsresponder to get it to obey that pref, though, so I’ll do a reboot to make sure that wasn’t the cause.

 

[frou]

It just now occurs to me that I might need to reload mdnsresponder to get it to obey that pref, though, so I’ll do a reboot to make sure that wasn’t the cause.

Definitely reboot. But after that, try this which will (slowly) find logs of all wakes in the prior 2 days:

log show --style syslog --last 2d | fgrep "Wake reason"

I think log lines mentioning "XHC" relate to impulses coming from external peripherals, and lines mentioning "RTC" relate to scheduled wakes set by e.g. mDNSResponder.