My Aspire TC-885 restarts without warning and without heavy CPU loads

headupeyesopen

From an Internet search, I've noticed that a number of users have posted the same kind of problem within the past few years. 

My issues are infrequent so far, but restarts can occur repeatedly in short order.  I've installed a temperature sensor, but all the readings are within bounds.  Restarts have occurred with heavy use and light use (e. g., one browser with three Websites open).  So far, they've only occurred when I've been working online. 

I bought my Acer Aspire TC-885-ACCFLi5 (TC-885_E) refurbished (changes listed below), but here is some info on the original machine:

I run it primarily with Ubuntu 20.04, but I have Win10 Pro as a dual boot. 

Refurbished with: 
Intel® Core™ i5-8400 Processor, 9M Cache, 2.80 to 4.00 GHz
256 GB SSD
16 GB DIMM DDR4 Synchronous 2666 MHz

I'm happy to supply any information for someone who might have an inkling (other than CPU temps, which seem to be fine) about the cause(s). 

I have over 30 years of PC experience, but PLEASE NOTE that I'm not a power user, developer or programmer. 

Thanks!

billsey

Do you get a blue screen before the restart? Does it happen in both Windows and Linux?

headupeyesopen

Hi Billsey,

No blue screen; from Linux, it just immediately blacks out like a soft boot and proceeds normally through the soft-boot sequence.  I only VERY rarely use Windows, so I can't comment on any shutdowns with that OS.   

I'm happy, however, to try anything you recommend, including using diagnostics that might identify the issue.

If it helps, I'm running Psensor 1.1.5 to monitor temps, CPU usage and available memory (http://wpitchoune.net/psensor/). 

FWIW, it happened right after I sent my last message.  I had this Website open and closed the browser, and I had the Linux terminal open, which I closed, but my hotspot was still active.  (Given the ISP issue here, I only use a hotspot or tether to get online.  I don't recall any other apps running besides the usual background programs and such.)  The machine then shut itself down. 

Also FWIW, the "info on the original machine" got left out:

Mfg Date:  2018/06/07

ttttt

@headupeyesopen

There are so many reasons for PC self restarts. Have you checked the system log to get some useful info there?

Don't know my personal experiences will help you but it maybe a possible solution.

One old desktop of mine had self restart problem for years, started with an average of once every 20 hours to the point of once every hour. Since I used SSD for it and the PC will restart in just about half minute, it didn't bother me much. I have tried RAM, graphics card, BIOS settings...etc. and the problem persisted. I concluded that the BIOS was going bad and decided to build a new desktop and ordered the parts. While having a new and more powerful PSU, I put the new PSU to the old PC having the self restarting problem and the problem was gone for three weeks while waiting for all new parts arrived and that new PSU being used for the new build later. My final conclusion was the old PSU loss efficiency through the years of dust buildup and could not provide enough power from time to time, even not under heavy CPU and graphics loads.
 
Try it if you can.

headupeyesopen

Hi TTTTT, and thanks. 

(1)  Yes, that's what I gathered from my online research about this kind of thing (RE "so many reasons"). 

(2)  Given my relative lack of expertise, I haven't checked the system log, but would be happy to do so.  I'll research how to do that for Ubuntu 20.04, which should be easy.  Once I do, shall I post pertinent log entries here?

(3)  I've wondered about the PSU; the machine as refurbished is, I assume, pretty clean.  At four years of age, is a PSU failure likely?  Regardless, can you recommend a Linux (or Win10) program for gauging the PSU function? 

(4)  One more thing that's highly technical to me: 
My Psensor program identifies the PCH as "Cannon Lake", but my actual CPU is Intel® Core™ i5-8400 Coffee Lake (14 nm).  The i5-8400 could be original equipment but my machine might have originally had a Core i3-8100 processor.  I understand that a motherboard PCH is not the same as a CPU, but . . .

Https://www.anandtech.com/show/13405/intel-10nm-cannon-lake-and-core-i3-8121u-deep-dive-review/ states that "the single processor from Intel built on 10nm falls under the Core 8th generation family, and is called the Core i3-8121U," If that was my stock CPU, https://www.pcgamer.com/intel-cpu-roadmap-all-the-lakes-from-14nm-to-7nm/ categorically pans the Cannon Lake 10-nm processor: 

"Cannon Lake (CNL, 10nm, 8th Gen Core, May 2018): . . . . Originally intended to launch in 2016, first demonstrated in 2017, and first shipped in very limited quantities in May 2018 [note my Mfg Date:  2018/06/07], Cannon Lake had more than a few issues. . . .

". . . . Intel released a 2-core/4-thread 'mobile' design, with the GPU portion of the chip disabled. Starting with a smaller chip is common for new process nodes, but disabling the integrated GPU in a mobile product speaks volumes. It was likely necessary to improve the number of functional chips Intel could get, which suggests incredibly poor yields. And even then, performance and power did not look good.

"Cannon Lake does include AVX512 instruction support, which can help in a few specific instances, but everything else is basically bad. Power, memory latency, and other elements were worse than with existing 14nm mobile designs. In retrospect, the difficulties caused by all the enhancements originally stuffed into Intel's 10nm process far outweighed the potential benefits. . . ."

So, could a Cannon Lake PCH be a potential cause of trouble in my case in spite of having a reliable i5 processor? 

Larryodie

My TC-895 (New Dec 2020) had restart problems with no blue screens and in stand-by it would start acting up with loud noises that may or not have been fan noise but it was scary loud. I saw other post that said to leave it on for a few days without going into sleep mode. It worked and has been perfect for a year plus. I'll see if I can find the post. 

ttttt

@headupeyesopen

Don't know if you use sleep mode for the TC-885.

For my case, I never used sleep mode for that old desktop.

Larryodie

This was basically my problem but it would sometimes reboot for no reason and not complete the boot at times. I did as the poster, left it on a few days and nights, All is well. 
https://community.acer.com/en/discussion/615207/aspire-tc-895-eb11-power-supply-audible-noise

JordanB

It’s most likely a power supply problem.  I would replace the power supply.  If you’re still under warranty, you can contact Acer.  

https://community.acer.com/en/discussion/577093/acer-tc-885-accfli5-rebooting-every-few-hours

headupeyesopen

I have no noise issues; the machine is extremely quiet.  When I first got it, the fan was so quiet that I thought it was dead.   

I have a 1-year warranty with the non-Acer refurbisher, but I hope to solve this issue without round-trip shipping or replacing a part (unless that's absolutely necessary). 

I don't suspect the power supply unless I can find a Linux (or Win10) program for gauging the PSU function.  Does anyone know of such a program? 

To repeat a couple other points, so that everyone reading this thread is up to date,

(1)  Given my relative lack of expertise, I haven't checked the system log, but would be happy to do so.  I'll research how to do that for Ubuntu 20.04, which should be easy.  Once I do, shall I post pertinent log entries here?

(2)  One more thing that's highly technical to me: 
My Psensor program identifies the PCH as "Cannon Lake", but my actual CPU is Intel® Core™ i5-8400 Coffee Lake (14 nm).  The i5-8400 could be original equipment but my machine might have originally had a Core i3-8100 processor.  I understand that a motherboard PCH is not the same as a CPU, but . . .

Https://www.anandtech.com/show/13405/intel-10nm-cannon-lake-and-core-i3-8121u-deep-dive-review/ states that "the single processor from Intel built on 10nm falls under the Core 8th generation family, and is called the Core i3-8121U," If that was my stock CPU, https://www.pcgamer.com/intel-cpu-roadmap-all-the-lakes-from-14nm-to-7nm/ categorically pans the Cannon Lake 10-nm processor: 

"Cannon Lake (CNL, 10nm, 8th Gen Core, May 2018): . . . . Originally intended to launch in 2016, first demonstrated in 2017, and first shipped in very limited quantities in May 2018 [note my Mfg Date:  2018/06/07], Cannon Lake had more than a few issues. . . .

". . . . Intel released a 2-core/4-thread 'mobile' design, with the GPU portion of the chip disabled. Starting with a smaller chip is common for new process nodes, but disabling the integrated GPU in a mobile product speaks volumes. It was likely necessary to improve the number of functional chips Intel could get, which suggests incredibly poor yields. And even then, performance and power did not look good.

"Cannon Lake does include AVX512 instruction support, which can help in a few specific instances, but everything else is basically bad. Power, memory latency, and other elements were worse than with existing 14nm mobile designs. In retrospect, the difficulties caused by all the enhancements originally stuffed into Intel's 10nm process far outweighed the potential benefits. . . ."

So, could a Cannon Lake PCH be a potential cause of trouble in my case in spite of having a reliable i5 processor? 

JordanB

You should suspect a power supply problem because it’s a power supply problem. 

You can get the power supply below for $53 on Amazon and your problem will be solved. 

https://www.evga.com/products/product.aspx?pn=110-BQ-0650-V1

headupeyesopen

Thank you, Jordan, but can you cite the reasons why you think it's a PSU problem? 

And/or can you (or anyone else reading this thread) point me in the direction of means by which I can evaluate the PSU? 

P. S. to TTTTT:  I occasionally use the suspend function; it works smoothly.  I haven't noticed a correlation between the spontaneous reboots and use of suspend.  Are you saying that your experience with your machine suggested or confirmed such a correlation? 

Larryodie

Does your Bios show the voltage outputs including the 5V that is derived from the 12V ?
 A bios battery change might also be worthwhile.

ttttt

@headupeyesopen

Since @Larryodie mentioned about his personal experience with sleep mode problem, you can try if that will apply to your case.
My experience with the old desktop did not involve sleep mode at all.

I am little confused, is your PC a four year old machine or is it still under one year warranty?

Currently, I tend to agree with @JordanB, not just because of we are in agreement about your case. As we know there maybe many reasons for PC self restart, I have seen enough cases that people reported that changing PSU solved the problem (including myself). A PSU need not be failed to give you a restart problem, just loss in efficiency will bring the power output marginally below the PC's requirement and causing the self restart problem intermittently.

Another common cause for PC restart is because of unreliable RAM. You can try just use one RAM module at a time and observe your PC.

headupeyesopen

Thanks for the clarification, TTTTT.  I couldn't tell who was speaking to whom above. 

My machine was manufactured about 4 years ago; it was refurbished recently by a company in St. Paul, MN, and I bought it in part because the refurbed machine has a one-year warranty. 

Thanks very much for the added info about the PSU and for the RAM suggestion.  Since no one has answered yet, should I suppose that there's no software known to this group that can evaluate the PSU while in operation? 

Larryodie

This is from my Bios on a TC-895-UA92

billsey

The PSU is of course one fairly high possibility. It would be quite worthwhile though to do a test to see if it happen in Windows as well as in Linux. If it does we have completely eliminated software as the issue. If it's stable long enough in Windows to point at a software issue then we need to look at what's running in Linux...

headupeyesopen

Good morning, billsey, Larryodie, and ttttt:

First off, thanks for the latest.  These reboots are, so far, so rare that I'd probably have to use Windows for hours before an incident occurred, but I understand that that would give us valuable info.  (FWIW, I switched to Linux a handful of years ago because I grew to hate Windows.  )

Second, I have log entries for a failure yesterday, and I can supply log entries for a normal reboot if we need/want to compare. 

I'll start with the "Important Log Messages" for a spontaneous reboot that occurred at 2:17 pm after a couple hours online with multiple Webpages open:

 2:18:10 PM gdm-session-wor: gkr-pam: unable to locate daemon control file
 2:17:59 PM bluetoothd: Failed to set mode: Blocked through rfkill (0x12)
 2:17:58 PM wpa_supplicant: nl80211: Failed to create a P2P Device interface p2p-dev-wlp0s20f3
 2:17:57 PM bluetoothd: Failed to set mode: Blocked through rfkill (0x12)
 2:17:55 PM kernel: sd 7:0:0:0: [sdc] Assuming drive cache: write through
 2:17:55 PM kernel: x86/cpu: SGX disabled by BIOS.

"Hardware Log Messages":

 2:17:55 PM kernel: ee1004 0-0053: 512 byte EE1004-compliant SPD EEPROM, read-only
 2:17:55 PM kernel: sd 8:0:0:0: [sdd] Attached SCSI removable disk
 2:17:55 PM kernel: scsi 8:0:0:0: Direct-Access     Generic- SD/MMC/MS PRO    1.00 PQ: 0 ANSI: 4
 2:17:55 PM kernel: sd 7:0:0:0: [sdc] Attached SCSI removable disk
 2:17:55 PM kernel: scsi 7:0:0:0: Direct-Access     Verbatim STORE N GO       5.00 PQ: 0 ANSI: 6
 2:17:55 PM kernel: hid-generic 0003:03F0:134A.0003: input,hidraw2: USB HID v1.11 Mouse [PixArt HP USB Optical Mouse] on usb-0000:00:14.0-3/input0
 2:17:55 PM kernel: scsi host8: usb-storage 1-9:1.0
 2:17:55 PM kernel: ums-realtek 1-9:1.0: USB Mass Storage device detected
 2:17:55 PM kernel: usb 1-14: New USB device strings: Mfr=0, Product=0, SerialNumber=0
 2:17:55 PM kernel: sd 6:0:0:0: [sdb] Attached SCSI removable disk
 2:17:55 PM kernel: scsi 6:0:0:0: Direct-Access     PNY      USB 3.0 FD       PMAP PQ: 0 ANSI: 6
 2:17:55 PM kernel: usb 1-14: new full-speed USB device number 6 using xhci_hcd
 2:17:55 PM kernel: scsi host7: usb-storage 1-7:1.0
 2:17:55 PM kernel: usb-storage 1-7:1.0: USB Mass Storage device detected
 2:17:55 PM kernel: usb 1-7: SerialNumber: CE00568150D7EE75
 2:17:55 PM kernel: scsi host6: usb-storage 2-6:1.0
 2:17:55 PM kernel: usb-storage 2-6:1.0: USB Mass Storage device detected
 2:17:55 PM kernel: usb 2-6: SerialNumber: 07009A29AAA4C261
 2:17:55 PM kernel: sr 3:0:0:0: Attached scsi generic sg1 type 5
 2:17:55 PM kernel: sd 1:0:0:0: [sda] Attached SCSI disk
 2:17:55 PM kernel: scsi 3:0:0:0: CD-ROM            Slimtype DVD A  DA8AESH   XA1M PQ: 0 ANSI: 5
 2:17:55 PM kernel: usb 1-1: new low-speed USB device number 2 using xhci_hcd
 2:17:55 PM kernel: sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
 2:17:55 PM kernel: scsi 1:0:0:0: Direct-Access     ATA      MTFDDAK256TBN-1A 0014 PQ: 0 ANSI: 5
 2:17:55 PM kernel: r8169 0000:01:00.0 enp1s0: renamed from eth0
 2:17:55 PM kernel: scsi host5: ahci
 2:17:55 PM kernel: ahci 0000:00:17.0: flags: 64bit ncq pm clo only pio slum part deso sadm sds apst
 2:17:55 PM kernel: i2c i2c-0: Successfully instantiated SPD at 0x53
 2:17:55 PM kernel: hub 2-0:1.0: 6 ports detected
 2:17:55 PM kernel: usb usb2: SerialNumber: 0000:00:14.0
 2:17:55 PM kernel: xhci_hcd 0000:00:14.0: Host supports USB 3.1 Enhanced SuperSpeed
 2:17:55 PM kernel: i2c i2c-0: 2/4 memory slots populated (from DMI)
 2:17:55 PM kernel: ahci 0000:00:17.0: controller can't do SNTF, turning off CAP_SNTF
 2:17:55 PM kernel: hub 1-0:1.0: 16 ports detected
 2:17:55 PM kernel: usb usb1: SerialNumber: 0000:00:14.0
 2:17:55 PM kernel: xhci_hcd 0000:00:14.0: hcc params 0x200077c1 hci version 0x110 quirks 0x0000000000009810
 2:17:55 PM kernel: i801_smbus 0000:00:1f.4: SMBus using PCI interrupt
 2:17:55 PM kernel: xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 1
 2:17:55 PM kernel: acpi PNP0C14:02: duplicate WMI GUID 05901221-D566-11D1-B2F0-00A0C9062910 (first instance was on PNP0C14:00)
 2:17:55 PM kernel: tty tty27: hash matches
 2:17:55 PM kernel: misc hpet: hash matches
 2:17:55 PM kernel: intel_pmc_core INT33A1:00:  initialized
 2:17:55 PM kernel: platform eisa.0: EISA: Detected 0 cards
 2:17:55 PM kernel: rtc_cmos 00:03: alarms up to one month, y3k, 242 bytes nvram
 2:17:55 PM kernel: thermal LNXTHERM:00: registered as thermal_zone0
 2:17:55 PM kernel: pcieport 0000:00:1c.0: DPC: error containment capabilities: Int Msg #0, RPExt+ PoisonedTLP+ SwTrigger+ RP PIO Log 4, DL_ActiveErr+
 2:17:55 PM kernel: pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff]
 2:17:55 PM kernel: pci_bus 0000:01: resource 2 [mem 0xa0000000-0xa00fffff 64bit pref]
 2:17:55 PM kernel: pci 0000:00:1c.0:   bridge window [mem 0xa0000000-0xa00fffff 64bit pref]
 2:17:55 PM kernel: system 00:08: Plug and Play ACPI device, IDs PNP0c02 (active)
 2:17:55 PM kernel: pnp 00:03: Plug and Play ACPI device, IDs PNP0b00 (active)
 2:17:55 PM kernel: system 00:02: Plug and Play ACPI device, IDs PNP0c02 (active)
 2:17:55 PM kernel: pci 0000:00:02.0: vgaarb: bridge control possible
 2:17:55 PM kernel: acpi LNXPOWER:09: Turning OFF
 2:17:55 PM kernel: pci 0000:00:1c.0:   bridge window [mem 0xa0000000-0xa00fffff 64bit pref]
 2:17:55 PM kernel: pci_bus 0000:00: root bus resource [mem 0xfc800000-0xfe7fffff window]
 2:17:55 PM kernel: acpi PNP0A08:00: _OSC: OS now controls [PCIeHotplug SHPCHotplug PME AER PCIeCapability LTR]

"System Log Messages": 

 2:18:47 PM kernel: EXT4-fs (sdb): mounted filesystem with ordered data mode. Opts: (null). Quota mode: none.
 2:18:25 PM kernel: audit: type=1326 audit(1647717505.185:60): auid=1000 uid=1000 gid=1000 ses=4 subj=snap.snap-store.ubuntu-software pid=2022 comm="pool-org.gnome." exe="/snap/snap-store/558/usr/bin/snap-store" sig=0 arch=c000003e syscall=93 compat=0 ip=0x7fe1841c13cb code=0x50000
 2:18:12 PM kernel: kauditd_printk_skb: 39 callbacks suppressed
 2:18:12 PM kernel: rfkill: input handler disabled
 2:18:12 PM kernel: FAT-fs (sdc): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
 2:18:12 PM kernel: IPv6: ADDRCONF(NETDEV_CHANGE): wlp0s20f3: link becomes ready
 2:18:12 PM kernel: wlp0s20f3: associated
 2:18:12 PM kernel: Lockdown: systemd-logind: hibernation is restricted; see man kernel_lockdown.7
 2:18:10 PM kernel: rfkill: input handler enabled
 2:18:10 PM kernel: Bluetooth: RFCOMM ver 1.11
 2:17:59 PM kernel: rfkill: input handler disabled
 2:17:59 PM kernel: Lockdown: systemd-logind: hibernation is restricted; see man kernel_lockdown.7
 2:17:58 PM kernel: loop22: detected capacity change from 0 to 8
 2:17:58 PM kernel: iwlwifi 0000:00:14.3: Conflict between TLV & NVM regarding enabling LAR (TLV = enabled NVM =disabled)
 2:17:57 PM kernel: r8169 0000:01:00.0 enp1s0: Link is Down
 2:17:57 PM kernel: Generic FE-GE Realtek PHY r8169-0-100:00: attached PHY driver (mii_bus:phy_addr=r8169-0-100:00, irq=MAC)
 2:17:57 PM kernel: NET: Registered protocol family 38
 2:17:57 PM kernel: Bluetooth: BNEP socket layer initialized
 2:17:57 PM kernel: audit: type=1400 audit(1647717477.137:11): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/sbin/cups-browsed" pid=795 comm="apparmor_parser"
 2:17:56 PM kernel: loop21: detected capacity change from 0 to 533936
 2:17:56 PM kernel: loop20: detected capacity change from 0 to 133552
 2:17:56 PM kernel: loop19: detected capacity change from 0 to 1968
 2:17:56 PM kernel: input: HDA Intel PCH HDMI/DP,pcm=10 as /devices/pci0000:00/0000:00:1f.3/sound/card0/input17
 2:17:56 PM kernel: snd_hda_codec_realtek hdaudioC0D0:      Line=0x15
 2:17:56 PM kernel: loop18: detected capacity change from 0 to 111080
 2:17:55 PM kernel: i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device
 2:17:55 PM kernel: Console: switching to colour frame buffer device 210x65
 2:17:55 PM kernel: fbcon: i915drmfb (fb0) is primary device
 2:17:55 PM kernel: loop17: detected capacity change from 0 to 3712
 2:17:55 PM kernel: snd_hda_intel 0000:00:1f.3: bound 0000:00:02.0 (ops i915_audio_component_bind_ops [i915])
 2:17:55 PM kernel: input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input7
 2:17:55 PM kernel: ACPI: video: Video Device [GFX0] (multi-head: yes  rom: no  post: no)
 2:17:55 PM kernel: [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0
 2:17:55 PM kernel: loop16: detected capacity change from 0 to 509456
 2:17:55 PM kernel: i915 0000:00:02.0: [drm] [ENCODER:108:DDI D/PHY D] is disabled/in DSI mode with an ungated DDI clock, gate it
 2:17:55 PM kernel: loop15: detected capacity change from 0 to 448512
 2:17:55 PM kernel: snd_hda_intel 0000:00:1f.3: enabling device (0000 -> 0002)
 2:17:55 PM kernel: loop14: detected capacity change from 0 to 507712
 2:17:55 PM kernel: Bluetooth: hci0: Found device firmware: intel/ibt-17-16-1.sfi
 2:17:55 PM kernel: intel_rapl_common: Found RAPL domain dram
 2:17:55 PM kernel: usbcore: registered new interface driver btusb
 2:17:55 PM kernel: iwlwifi 0000:00:14.3 wlp0s20f3: renamed from wlan0
 2:17:55 PM kernel: intel_tcc_cooling: Programmable TCC Offset detected
 2:17:55 PM kernel: ieee80211 phy0: Selected rate control algorithm 'iwl-mvm-rs'
 2:17:55 PM kernel: loop13: detected capacity change from 0 to 868688
 2:17:55 PM kernel: mei_hdcp 0000:00:16.0-b638ab7e-94e2-4ea2-a552-d1c54b627f04: bound 0000:00:02.0 (ops i915_hdcp_component_ops [i915])
 2:17:55 PM kernel: iwlwifi 0000:00:14.3: base HW address: 74:70:fd:e2:95:87
 2:17:55 PM kernel: i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/kbl_dmc_ver1_04.bin (v1.4)
 2:17:55 PM kernel: Console: switching to colour dummy device 80x25
 2:17:55 PM kernel: thermal thermal_zone2: failed to read out thermal zone (-61)
 2:17:55 PM kernel: loop12: detected capacity change from 0 to 605624

headupeyesopen

And here's the BIOS Advanced info after a manual restart at about 7:45 this morning: 

billsey

That is all looking pretty normal to me. The 2:17:55 PM all seem to be a normal startup, so entered after the crash. Was there anything in the logs closer to 2:17:00? The BIOS displayed temperatures are also normal for the very little load on a system in that state. I'd expect them to be more like CPU temps of 50-60C under normal running, and climbing to 80C or so when under heavy use. A forced shutdown shouldn't occur unless you hit 100C...

headupeyesopen

On the Linux side, I don't have the option to get the BIOS info without a restart.  If I've been working the PC for a while at some load, should I restart and submit another screen shot of the BIOS readings, or would they only show temps reflecting a small load after the restart? 

If a spontaneous restart occurs again, I'll try to get the BIOS info during that restart.  I wasn't quick enough to do that the other day. 

As for the logs, when I downloaded the Important, Hardware and System logs, they only showed times regarding the reboot event (i. e., nothing earlier).  If/when it happens again, I'll check the entire list of entries (all types thereof), which should provide info about the times just before the reboot. 

Through the psensor program, I can keep track of temps for the CPU and related hardware.  I've not seen any excessive temperatures, loss of free memory,  or CPU usage, but I just ordered the program to log those entries every 60 s (frequent enough?) in case I miss something.