My Mac Pro spontaneously restarts

Sign me into this club too! I purchased my Mac Pro in early 2008 (it was built in late 2007) and it is still running Leopard (OSX 10.5.8). Despite it's age, the computer has been operating exceptionally well until the past week or so when it started the spontaneous restarts. They typically occurred within the first 1/2 hour after the first start in the morning; but once the computer became stable, it usually ran without incident every day for about another 10 to 12 hours. I don't intend to spend much money to replace any components so I have been working through this thread trying any of the simple (and free) fix solutions. For the benefit of others, here's what I've found:

1. I don't think it has anything to do with heat. The problem occurs primarily when the computer is cold, and it has not occurred during hours of online gaming later in the day when it is running very hot.

2. Unplugging to reset the SMC did not help, nor did reseting the PRAM.

3. I used memtest to test the RAM, and it passed.

4. I used the extended test on the AHT and it passed.

5. I took a good look at the motherboard, etc for wonky capacitors and everything looks okay.

6. I switched and jiggled cables, power bars, peripherals, etc and it made no difference to the frequency of restarts.

Previous posts have suggested that the memory risers (particularly the lower one) might be the source of the problem, so yesterday I decided to give it a good dusting and reseat the RAM risers. Something interesting happened. After cleaning and removing and replacing the risers, I tried to start up the computer. The fan when into hurricane mode but it would not boot. After a couple attempts to start it, I opened it up and removed and reseated the risers again; once more it would not boot. I repeated again; no boot. Finally, I pulled out the bottom riser and tried to start it; it booted up perfectly and seemed stable. After about 1/2 hour, I shut it down and put the bottom riser back in. Miraculously, it booted with both risers loaded. It is running fine today. *fingers crossed*

I'm not sure what all this means. As in previous posts, I think that bottom riser has something to do with the spontaneous restarts. Perhaps, all the removing and replacing cleaned the contacts; or maybe something got giggled in the process. If the problem comes back, I intend to focus on the risers again: switching and removing etc. I know this is an ancient thread but it has been useful to me, so I'll post any updates to my situation.

Interesting! I had some similar RAM problems with mine, where it was working fine with both risers, then later on it wouldn't boot with the same config but would boot with either/or.

As you may have read earlier, I parted mine out and sold it on ebay (one of the fans sold as recently as this week!). I advise you to do the same so you don't waste any more time on this thing... It's going to get worse, not better.

For this MDS error, I'd suggest you just reset your Spotlight indexer.

Open Terminal and paste the following:

sudo mdutil -avE

I have been having this issue on and off for a few years. I solved it as follows at a point where I felt it had something to do with the RAM I had installed. I first copped it was something to do with RAM when I checked the 'about this Mac' in the menu and saw that the machine was not recognising all my installed RAM when it was doing the on and off routine.

So - I opened the machine and removed all the RAM and then re-installed it again. As you are reinstalling each RAM chip, reseat it in and out of the slot two or three times. This seemed to clear the issue for me. I don't know exactly what caused this issue but reseating the RAM seems to solve it for me when it occurs. Regards.

I've read over this entire thread again, and it looks like there is more than one issue which can trigger a restart: loose hardware (i.e. chip creep from dust), bad RAM, dying or somehow defective batteries, and, as in my case, CPU overheating. I tried many things, but the one that finally worked for me was when I started using SMC Fan Control from http://www.eidac.de . Keeping the unit cool really made the difference for me. I also changed out my dust-accumulating AT Radeon x1900 512M video card for a ATI Radeon 5770 1 GB. The old video card had to be taken out and carefully cleaned every year or so, but I did that before using SMCFan Control and although experiencing less restarts with the new card, the problem entirely went away once I started bumping up all the fan speeds.

This past summer (2014) I finally took the plunge and purchased a *new* Mac Pro 3,1 (early 2008). Ha ha ha. I have had no problems with restarting. The old Mac Pro 1,1 now resides in the more dusty but much cooler basement and so far my son hasn't complained about any restarts.

The Mac Pro series, in my humble opinion, despite the frustration evinced of this thread, represents Apple's finest and most versatile desktop computer.

I can't believe this forum started in 2009 and goes on until 2015. I bought a Mac Pro, 6-cores, which I have had for about 2 months. It spontaneously rebooted itself a couple of times since, which I thought was odd, but then last night I was viewing email in Safari/Yahoo when it rebooted itself 3 times in a row. I put the Mac to sleep after the 3rd reboot and later I checked it and it seemed all right. It hasn't happened since so far. I will probably be taking it to the local Apple authorized repair shop since it is still under warranty. I might wait a few days to see if it happens more. I have had a lot of strange glitches since the minute I plugged this Mac in on day one. My 2009 Mac Pro rarely gave me any problems the whole time I had it. I am starting to wish I had kept it.

There are so many replies, I don't know if anyone has solved this, but I have found something that has worked for me, twice, on my Mac Pro Tower 2008, OS 10.6.8. Like everyone else, my Mac was restarting by itself over and over. Here's what I did: 1) Clean up the dust inside (canned air and wiping down the flat surfaces that had a ton of dust on them. 2) Remove the video card and reseat it. Pulling the card out can be a bit of a trick, it can seem stuck, but you just have to pull firmly (ok, don't forget to unscrew the little screws that hold it in, and don't drop 'em!). Just pull it 'up' a few inches away, enough to pull it free of the contacts.

I suggest immediately reseating it, rather than pulling the card out to inspect and then realize that re-positioning it is awkward, especially if you haven't pulled the vid card before. Old pros can ignore this recommend.

This worked for me a few years ago and just recently (Late April 2015) the problem resurfaced. I can't say that cleaning did the trick, but it was awfully dusty inside my Mac anyway. Perhaps related (or not!), I've replaced my video card twice now, so I'm on my third vid card. They just don't seem to last.

I don't guarantee anything, but if you haven't tried this, give it a shot and best of luck to you!

hmm i bought this system in the states last november an i live in trinidad ( the caribbean). so what else i can do

and yes i still have warranty but i can't find the bill wayyyyy what a thing

HI EVERYONE!

I just started having this problem, after years of my used 3,1 8-core working just fine. Recently installed very cheap RAM, but haven't had a problem for the first few months. Restarted a couple times in the past week, and today just keeps restarting nonstop.

Seemed like a PSU issue (as I read in this thread) so I unplugged everything from the back. I'm using two 20" cinema displays, probably the 2004-2006 models. Problem still happened with both displays connected, but all firewire and usb stuff unplugged. I unplugged one cinema display and it started up and ran no problem. While it was still running, I connected the second display and it rebooted at that instant.

Started up again and checked RAM, all units registering. Was about to plug in the monitor again to see if it would be consistent, but the computer restarted the instant I bumped it with my body, reaching over to the backside.

Read an earlier post about the videocard and dust. It's not very dusty inside my computer but I'll give it a shot. Sad that I wasn't able to find a consistent trigger.

New info! I started playing with the monitor cables, and it restarted like 4 times in a row, each time I jiggled a cable, regardless of how "started-up" the computer was. I removed the two sticks of cheap RAM I had installed, and started it up in exactly the same condition: no problems. Jiggled monitor cables, no problems. Mounted my 2 other internal HD's and connected 3 externals, no problems. Computer seems to be ever-so-slightly zippier. But maybe that's my imagination.

SO, I'm thinking that in my case the crap RAM was causing a power draw, such that every time the PSU needed to adapt more voltage, it would starve the system. I'll reply if I get another restart, but otherwise consider that this fix worked for me. Suffice it to say that you may way to stay away from "NEMIX" brand memory.

I seem to be having similar problems to most of those in the post:

I am getting constant kernel panics that randomly restart my mid-2010 MacBook Pro. I am running OS X 10.11.1 El Capitan (successfully otherwise). These crashes happened in El Capitan as well as in Mountain Lion. I have trouble shot it in so many ways but I am at my wits end. Running the Apple Hardware Test I get the following, very unhelpful code: -3403D. Sometimes it restarts 4 or 5 times within an hour. Sometimes it will run the whole day without crashing. The kernel panics might be due to the gfx card (Built-in Intel HD Graphics 288 MB, NVIDIA GeForce GT 330M PCle). When I manually make the computer run in Integrated Only it seems to be better, but if the computer falls asleep it will change back to Dynamic Switching and inevitably my computer crashes. Is there a way I can make it permanently in Integrated only (I don't know if this is bad or not...)? Or can I remove the PCle NVIDIA? This may not be the only issue but I am requesting some help in this... I pasted the first of 4 panic reports from this morning below, just in case you need it. Thank you...

Anonymous UUID: F2B4A072-D1FD-907E-A948-57CAC9B1E927

Wed Nov 25 07:40:06 2015

*** Panic Report ***

panic(cpu 0 caller 0xffffff7fa0045bad): "GPU Panic: [<None>] 5 3 7f 0 0 0 0 3 : NVRM[0/1:0:0]: Read Error 0x00000100: CFG 0xffffffff 0xffffffff 0xffffffff, BAR0 0xd2000000 0xffffff9138d8a000 0x0a5480a2, D0, P2/4\n"@/Library/Caches/com.apple.xbs/Sources/AppleGraphicsControl/AppleGraphic sControl-3.11.33.1/src/AppleMuxControl/kext/GPUPanic.cpp:127

Backtrace (CPU 0), Frame : Return Address

0xffffff914f022ed0 : 0xffffff801cee5307

0xffffff914f022f50 : 0xffffff7fa0045bad

0xffffff914f023030 : 0xffffff7f9dbe9fa4

0xffffff914f0230f0 : 0xffffff7f9dcb6add

0xffffff914f023130 : 0xffffff7f9dcb6b48

0xffffff914f0231b0 : 0xffffff7f9df3ba23

0xffffff914f023320 : 0xffffff7f9dcdab79

0xffffff914f023340 : 0xffffff7f9dbf0cfd

0xffffff914f0233f0 : 0xffffff7f9dbee690

0xffffff914f0235f0 : 0xffffff7f9dbf0141

0xffffff914f0236c0 : 0xffffff7f9f4cba47

0xffffff914f023790 : 0xffffff7f9f4f61df

0xffffff914f023820 : 0xffffff7f9f4de201

0xffffff914f023880 : 0xffffff7f9f4deb22

0xffffff914f0238d0 : 0xffffff7f9f4dee77

0xffffff914f023940 : 0xffffff7f9f4df6f1

0xffffff914f023980 : 0xffffff7f9f4ac4e0

0xffffff914f023b00 : 0xffffff7f9f4ab03b

0xffffff914f023b50 : 0xffffff801d4e3016

0xffffff914f023b80 : 0xffffff801d4e48e0

0xffffff914f023be0 : 0xffffff801d4e1967

0xffffff914f023d20 : 0xffffff801cfa07d0

0xffffff914f023e30 : 0xffffff801cee9aa3

0xffffff914f023e60 : 0xffffff801cecd478

0xffffff914f023ea0 : 0xffffff801cedcfd5

0xffffff914f023f10 : 0xffffff801cfc13aa

0xffffff914f023fb0 : 0xffffff801cff4b36

Kernel Extensions in backtrace:

com.apple.driver.AppleMuxControl(3.11.33b1)[FF6CE9C5-9D8F-3A48-9D10-2BB9C2DDD22 7]@0xffffff7fa0037000->0xffffff7fa004afff

dependency: com.apple.driver.AppleGraphicsControl(3.11.33b1)[4ADB751E-5208-3DA7-A8C3-E9EC07 263B16]@0xffffff7fa002f000

dependency: com.apple.iokit.IOACPIFamily(1.4)[CBAE26D8-0ACB-3C1F-8347-FDCA67EC40B3]@0xfffff f7f9d9b4000

dependency: com.apple.iokit.IOPCIFamily(2.9)[8E5F549E-0055-3C0E-93F8-E872A048E31B]@0xffffff 7f9d72d000

dependency: com.apple.iokit.IOGraphicsFamily(2.4.1)[48AC8EA9-BD3C-3FDC-908D-09850215AA32]@0 xffffff7f9db3c000

dependency: com.apple.driver.AppleBacklightExpert(1.1.0)[5CB7D4B7-B100-34EE-BD40-1EC07E865C 67]@0xffffff7fa0032000

com.apple.nvidia.classic.NVDAResmanTesla(10.0)[05FC5D7E-BB0B-3232-BBBD-8A49B687 0D8B]@0xffffff7f9db93000->0xffffff7f9de08fff

dependency: com.apple.iokit.IOPCIFamily(2.9)[8E5F549E-0055-3C0E-93F8-E872A048E31B]@0xffffff 7f9d72d000

dependency: com.apple.iokit.IONDRVSupport(2.4.1)[814A7F4B-03EF-384A-B205-9840F0594421]@0xff ffff7f9db83000

dependency: com.apple.iokit.IOGraphicsFamily(2.4.1)[48AC8EA9-BD3C-3FDC-908D-09850215AA32]@0 xffffff7f9db3c000

com.apple.nvidia.classic.NVDANV50HalTesla(10.0)[56199CA6-3C8D-3EBB-B5EF-7B1B467 8ACF9]@0xffffff7f9de13000->0xffffff7f9e0c0fff

dependency: com.apple.nvidia.classic.NVDAResmanTesla(10.0.0)[05FC5D7E-BB0B-3232-BBBD-8A49B6 870D8B]@0xffffff7f9db93000

dependency: com.apple.iokit.IOPCIFamily(2.9)[8E5F549E-0055-3C0E-93F8-E872A048E31B]@0xffffff 7f9d72d000

com.apple.GeForceTesla(10.0)[49982DF3-8146-3BD0-AD3F-A7E7AB5ACBB5]@0xffffff7f9f 499000->0xffffff7f9f564fff

dependency: com.apple.iokit.IOPCIFamily(2.9)[8E5F549E-0055-3C0E-93F8-E872A048E31B]@0xffffff 7f9d72d000

dependency: com.apple.iokit.IONDRVSupport(2.4.1)[814A7F4B-03EF-384A-B205-9840F0594421]@0xff ffff7f9db83000

dependency: com.apple.iokit.IOGraphicsFamily(2.4.1)[48AC8EA9-BD3C-3FDC-908D-09850215AA32]@0 xffffff7f9db3c000

dependency: com.apple.nvidia.classic.NVDAResmanTesla(10.0.0)[05FC5D7E-BB0B-3232-BBBD-8A49B6 870D8B]@0xffffff7f9db93000

BSD process name corresponding to current thread: WindowServer

Mac OS version:

15B42

Kernel version:

Darwin Kernel Version 15.0.0: Sat Sep 19 15:53:46 PDT 2015; root:xnu-3247.10.11~1/RELEASE_X86_64

Kernel UUID: AB5FC1B4-12E7-311E-8E6F-9023985D8C1D

Kernel slide: 0x000000001cc00000

Kernel text base: 0xffffff801ce00000

__HIB text base: 0xffffff801cd00000

System model name: MacBookPro6,2 (Mac-F22586C8)

System uptime in nanoseconds: 251590445774

last loaded kext at 64407918897: com.apple.driver.AudioAUUC 1.70 (addr 0xffffff7f9f78b000, size 32768)

loaded kexts:

1. com.apple.driver.AudioAUUC 1.70
2. com.apple.driver.AppleHWSensor 1.9.5d0
3. com.apple.driver.AppleTyMCEDriver 1.0.2d2
4. com.apple.driver.AGPM 110.20.21
5. com.apple.filesystems.autofs 3.0
6. com.apple.driver.AppleOSXWatchdog 1
7. com.apple.driver.AppleMikeyHIDDriver 124
8. com.apple.driver.AppleUpstreamUserClient 3.6.1
9. com.apple.driver.AppleHDAHardwareConfigDriver 272.50.31
10. com.apple.driver.pmtelemetry 1
11. com.apple.driver.AppleIntelHDGraphics 10.0.0
12. com.apple.driver.AppleHDA 272.50.31
13. com.apple.GeForceTesla 10.0.0
14. com.apple.iokit.IOUserEthernet 1.0.1
15. com.apple.driver.AppleMikeyDriver 272.50.31
16. com.apple.iokit.IOBluetoothSerialManager 4.4.2f1
17. com.apple.Dont_Steal_Mac_OS_X 7.0.0
18. com.apple.driver.AppleHV 1
19. com.apple.driver.AppleIntelSlowAdaptiveClocking 4.0.0
20. com.apple.driver.AppleFIVRDriver 4.1.0
21. com.apple.driver.AppleIntelHDGraphicsFB 10.0.0
22. com.apple.driver.AppleBacklight 170.8.1
23. com.apple.driver.AppleMCCSControl 1.2.13
24. com.apple.nvidia.NVDAStartup 10.0.6
25. com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport 4.4.2f1
26. com.apple.driver.AppleSMCLMU 208
27. com.apple.driver.AppleMuxControl 3.11.33b1
28. com.apple.driver.ACPI_SMC_PlatformPlugin 1.0.0
29. com.apple.driver.AppleSMCPDRC 1.0.0
30. com.apple.driver.AppleLPC 3.1
31. com.apple.driver.SMCMotionSensor 3.0.4d1
32. com.apple.driver.AppleUSBTCButtons 245.4
33. com.apple.iokit.IOBluetoothUSBDFU 4.4.2f1
34. com.apple.driver.AppleUSBTCKeyEventDriver 245.4
35. com.apple.driver.AppleUSBTCKeyboard 245.4
36. com.apple.driver.AppleUSBStorageCoexistentDriver 3.7.1
37. com.apple.driver.AppleUSBCardReader 3.7.1
38. com.apple.driver.AppleIRController 327.5
39. com.apple.driver.CoreStorageFsck 517
40. com.apple.driver.AppleFileSystemDriver 3.0.1
41. com.apple.AppleFSCompression.AppleFSCompressionTypeDataless 1.0.0d1
42. com.apple.AppleFSCompression.AppleFSCompressionTypeZlib 1.0.0
43. com.apple.BootCache 37
44. com.apple.iokit.SCSITaskUserClient 3.7.7
45. com.apple.iokit.IOAHCIBlockStorage 2.8.0
46. com.apple.driver.AppleFWOHCI 5.5.2
47. com.apple.driver.AirPort.Brcm4331 800.20.24
48. com.apple.driver.AirPort.Brcm4360 1010.14.1a4
49. com.apple.driver.AppleAHCIPort 3.1.5
50. com.apple.driver.usb.AppleUSBEHCIPCI 1.0.1
51. com.apple.iokit.AppleBCM5701Ethernet 10.1.11
52. com.apple.driver.usb.AppleUSBUHCIPCI 1.0.1
53. com.apple.driver.AppleHPET 1.8
54. com.apple.driver.AppleSmartBatteryManager 161.0.0
55. com.apple.driver.AppleACPIButtons 4.0
56. com.apple.driver.AppleRTC 2.0
57. com.apple.driver.AppleSMBIOS 2.1
58. com.apple.driver.AppleACPIEC 4.0
59. com.apple.driver.AppleAPIC 1.7
60. com.apple.driver.AppleIntelCPUPowerManagementClient 218.0.0
61. com.apple.nke.applicationfirewall 163
62. com.apple.security.quarantine 3
63. com.apple.security.TMSafetyNet 8
64. com.apple.driver.AppleIntelCPUPowerManagement 218.0.0
65. com.apple.AppleGraphicsDeviceControl 3.11.33b1
66. com.apple.kext.triggers 1.0
67. com.apple.driver.DspFuncLib 272.50.31
68. com.apple.kext.OSvKernDSPLib 525
69. com.apple.nvidia.classic.NVDANV50HalTesla 10.0.0
70. com.apple.nvidia.classic.NVDAResmanTesla 10.0.0
71. com.apple.iokit.IOSurface 108.0.1
72. com.apple.iokit.IOSerialFamily 11
73. com.apple.driver.CoreCaptureResponder 1
74. com.apple.iokit.IOSlowAdaptiveClockingFamily 1.0.0
75. com.apple.driver.AppleSMBusController 1.0.14d1
76. com.apple.iokit.IOBluetoothHostControllerUSBTransport 4.4.2f1
77. com.apple.iokit.IOBluetoothFamily 4.4.2f1
78. com.apple.iokit.IOFireWireIP 2.2.6
79. com.apple.driver.AppleBacklightExpert 1.1.0
80. com.apple.iokit.IONDRVSupport 2.4.1
81. com.apple.driver.AppleGraphicsControl 3.11.33b1
82. com.apple.driver.IOPlatformPluginLegacy 1.0.0
83. com.apple.driver.AppleSMBusPCI 1.0.14d1
84. com.apple.driver.AppleHDAController 272.50.31
85. com.apple.iokit.IOGraphicsFamily 2.4.1
86. com.apple.iokit.IOHDAFamily 272.50.31
87. com.apple.iokit.IOAudioFamily 204.1
88. com.apple.vecLib.kext 1.2.0
89. com.apple.driver.IOPlatformPluginFamily 6.0.0d7
90. com.apple.driver.AppleSMC 3.1.9
91. com.apple.driver.usb.IOUSBHostHIDDevice 1.0.1
92. com.apple.driver.AppleUSBMultitouch 250.4
93. com.apple.iokit.IOUSBMassStorageClass 4.0.0
94. com.apple.iokit.IOSCSIBlockCommandsDevice 3.7.7
95. com.apple.iokit.IOUSBMassStorageDriver 1.0.0
96. com.apple.iokit.IOUSBHIDDriver 900.4.1
97. com.apple.driver.usb.AppleUSBHostCompositeDevice 1.0.1
98. com.apple.driver.CoreStorage 517
99. com.apple.driver.usb.AppleUSBHub 1.0.1
100. com.apple.iokit.IOSCSIMultimediaCommandsDevice 3.7.7
101. com.apple.iokit.IOBDStorageFamily 1.8
102. com.apple.iokit.IODVDStorageFamily 1.8
103. com.apple.iokit.IOCDStorageFamily 1.8
104. com.apple.driver.AppleXsanScheme 3
105. com.apple.iokit.IOAHCISerialATAPI 2.6.2
106. com.apple.iokit.IOSCSIArchitectureModelFamily 3.7.7
107. com.apple.driver.AppleUSBMergeNub 900.4.1
108. com.apple.iokit.IOFireWireFamily 4.5.8
109. com.apple.iokit.IO80211Family 1101.24
110. com.apple.driver.corecapture 1.0.4
111. com.apple.iokit.IOAHCIFamily 2.8.0
112. com.apple.iokit.IOUSBFamily 900.4.1
113. com.apple.iokit.IOEthernetAVBController 1.0.3b3
114. com.apple.driver.mDNSOffloadUserClient 1.0.1b8
115. com.apple.iokit.IONetworkingFamily 3.2
116. com.apple.driver.usb.AppleUSBUHCI 1.0.1
117. com.apple.driver.usb.AppleUSBEHCI 1.0.1
118. com.apple.iokit.IOUSBHostFamily 1.0.1
119. com.apple.driver.AppleUSBHostMergeProperties 1.0.1
120. com.apple.driver.AppleEFINVRAM 2.0
121. com.apple.driver.AppleEFIRuntime 2.0
122. com.apple.iokit.IOHIDFamily 2.0.0
123. com.apple.iokit.IOSMBusFamily 1.1
124. com.apple.security.sandbox 300.0
125. com.apple.kext.AppleMatch 1.0.0d1
126. com.apple.driver.AppleKeyStore 2
127. com.apple.driver.AppleMobileFileIntegrity 1.0.5
128. com.apple.driver.AppleCredentialManager 1.0
129. com.apple.driver.DiskImages 415
130. com.apple.iokit.IOStorageFamily 2.1
131. com.apple.iokit.IOReportFamily 31
132. com.apple.driver.AppleFDEKeyStore 28.30
133. com.apple.driver.AppleACPIPlatform 4.0
134. com.apple.iokit.IOPCIFamily 2.9
135. com.apple.iokit.IOACPIFamily 1.4
136. com.apple.kec.Libm 1
137. com.apple.kec.pthread 1
138. com.apple.kec.corecrypto 1.0

AngelInfinite

your issue is with the MacBOOK Pro 6,2 -- a notebook computer. It has nothing in common with the Mac Pro 42lb silver towers on this thread.

Your problem appears to be with the graphics on that MacBook Pro. There were some well-know Latent Defects with the Graphics chips on some of those MacBooks, and there was a substantial recall program. It has long since expired.

If you cannot get this problem to resolve, you may get relief by:

• Having the graphics chip or the entire motherboard replaced.

• Dropping back to an older Mac OS X.

• using gfxcardstatus third-party utility to force Integrated graphics only, and refrain from attaching an external display.

.

Thank you so much. Apologies for posting on the wrong thread - Apple Support newbie. The problems happened in Mountain Lion as well, so I'm not sure that will help. I will definitely try the gfx utility first. Really appreciate the quick response.

My 2013 Mac Pro spontaneously rebooted many times almost from the start. I bought it last January 2015. Recently, I had gone 6 months without having this problem then suddenly it came back. I have been keeping a journal of each time my Mac reboots itself spontaneously and trying to remember what I had been doing. One thing, lately, I have been downloading with a Download Manager in the background or else trying to view or move a downloaded file when my Mac would freeze then reboot. If I tried to continue what I was doing, it would restart again. I would have to delete the "bad" files or stop downloading with the Download Manager (iGetter). This has been since El Capitan that the problem has come back.

I just read an article about El Capitan and that it uses something called SIP System Integrity Protection. Some software does not work well with it. This SIP is supposed to help prevent malware from getting into my system, but there is a way in Terminal to disable SIP. I am thinking I may try disabling it and see if my Download Manager works without these restarts. Will report on that later.